This is a situation where the wording of the law is unclear, so "meaning" must be created out of supposed judicial intent, which is always a dangerous enterprise. Relevant case law is State v. Rabanales-Ramos, under a prior version of the law. In that case, the issue arises as to the meaning of "use", and the court says
the context of ORS 811.507(2), including the other provisions of ORS
811.507, suggests that the meaning of the term “uses” in ORS 811.507(2) is limited to use of a mobile communication device for the purpose of voice or text communication. See PGE, 317 Or at 611
(context of a statutory provision includes other provisions of the
same statute). First, we note that the definition of “mobile
communication device” set forth in ORS 811.507(1) is “a text messaging
device or a wireless, two-way communication device designed to receive
and transmit voice or text communication.” (Emphases added.) That
definition suggests that the activity that the legislature intended to
address was using a mobile communication device for voice or text
communication. The legislature did not include in its definition of
“mobile communication device” a device incapable of receiving and
transmitting voice or text communication, such as a hand-held GPS
mapping device or music-playing device, which suggests that the
legislature did not intend to broadly prohibit the use of any mobile
device for any purpose; rather, the legislature intended to address
the specific act of communicating, by voice or text, using a mobile
communication device. Furthermore, the lack of any reference in the
statute to possible functions of a mobile communication device apart
from receiving and transmitting voice or text communication, such as
playing music or getting directions, suggests that the legislature did
not contemplate the application of ORS 811.507 to such functions.
The definitions in the earlier law included:
“(a) ‘Hands-free accessory’ means an attachment or built-in feature
for or an addition to a mobile communication device, whether or not
permanently installed in a motor vehicle, that when used allows a
person to maintain both hands on the steering wheel.
“(b) ‘Mobile communication device’ means a text messaging device or a
wireless, two-way communication device designed to receive and
transmit voice or text communication.
By framing the law in terms of "mobile communications device", it was deemed by the court that the legislature intended the restriction to be about communicative uses.
The recent change in the law clearly expands the scope of the prohibition, with respect to uses, because it now refers to "mobile electronic devices" and explicitly mentions navigation. Then the question is what constitutes a "hands-free device". Regarding the cup-holder option, the question would be whether a cup-holder is "an attachment or built-in feature for or an addition to a mobile electronic device". A plain language analysis would indicate that a cup-holder is not an attachment or built-in feature for an electronic device, nor is it an addition to a mobile electronic device. However, a dash mount would be (though legislative intent may have been more restrictive). To override the plain words of a statute, there must be compelling evidence of a contrary legislative intent.
Additionally, we must assign some meaning to the changed wording "gives a person the ability to keep", as contrasted with allowing to maintain – we have to assume that the legislature meant something, in changing those words. This suggests that the hands-free device has to actively contribute to the ability to keep both hands on the wheel, in the way that a blue tooth device would. Actually holding a cell phone in your hands would also "allow" a person to have both hands on the wheel, but such an action conflicts with the plain meaning of "hands-free". We have to conclude, then, that the legislature did not just mean "as long as both hands are on the wheel".
There is testimonial evidence, from 6-22 (and similar support and opposition during that hearing), that the Senate was aware of the interpretation that the law "will punish drivers who currently make an effort to utilize their mobile electronics in the least-distracting means possible, by mounting them in lieu of an in-dash display", but the bill remain un-amended. We can contrast the fact that nothing was changed in any version of the bill with respect to the phone-qua-GPS issue in light of testimony objecting to restricting such temporary dash-mount use, to the fact that there was also testimony pertaining to limitations on radio communication under the House version of the bill, whereby the amended Senate version and the final version expanded subsection (2) to allow such uses. As this (early) testimony indicates, "if it is not permanently installed, then it is prohibited" (Senator Prozanski in his testimony around 5:30 in confirms the distinction between built-in devices vs. cell phones and the like, in that a built-in device is not a "mobile electronic device", thus not restricted.
In other words, we can conclude that the legislature was aware that the law would restrict use of dash-mount devices as surrogates for built-in GPS (which is allowed), and chose not to change the language of the bill: that such a restriction would not be an unintended consequence. As we know, legislative-intent arguments are often facile, but the court did rely on such facile arguments to reach the earlier conclusion that the law only addressed communicative uses.