Parking laws are very much a matter of local municipal law. There does not appear to be a general rule mandating signage on a Canada-wide basis.
I examined the parking code of th4e City of Hamilton, Ontario (BY-LAW NO. 01-218) This is some 56 pages long, and some provisions specify signage, and some do not.
For example section (9)(1) provides:
No person shall on any day except a holiday, park a vehicle on any highway or portion of highway listed in schedule 6, for a longer time than indicated therein, during the periods specified therein, provided suitable signs are erected and maintained. (Emphasis added)
However, section 11 (2) provides:
The Council may designate a highway or part highway as a permit parking zone by prohibiting parking on the said highway or part highway except by valid permit under the provisions of this Section, and said highway shall be listed in Schedule 12 of this by-law.
Section 11 (12) provides:
No person shall park a vehicle in a permit parking zone, who is not the eligible applicant to whom a parking permit has been issued and is in force ...
No provision in section 11 mentions any sign to be posted to notify people of the permit requirements. Apparently being listed in the schedule is sufficient.
Section 12 (2) provides:
Subject to subsections (3) and (4), no person shall park any vehicle or permit a vehicle to remain parked on any roadway or shoulder where such parking or stopping is normally permitted except:
... {provisions for parking in the direction of traffic movement}
save and except where suitable signs are erected and maintained indicating that perpendicular or angle parking is required ...
Section 12 (5) has a variety of parking restrictions, including prohibiting parking
12 (5) (c) Within six (6) metres (20 feet) of an entrance to any armouries, drill hall, armouries yard, hospital, theatre, church, hotel, railroad station, bus terminal or other place of assembly, and provided, that except that in the case of an athletic field or fair grounds, this prohibition shall apply only while an assembly is therein, and for one hour immediately preceding and following such assembly; (no sigage requirement listed)
12 (5) (d) Where temporary "No Parking" signs are erected, placed or posted along any highway or part of a highway ...
12 (5) (e) Along that part of any highway which abuts an unfenced playground or unfenced school playground between the hours of 7:00 a.m. and 6:00 p.m. of any day except a Sunday, provided that suitable signs are erected and maintained;
12 (5) (k) (ii) On any boulevard, provided that this shall not prohibit the parking of a vehicle: ... where parking is specifically permitted by an agreement between the City and the owner of the abutting lands or a license granted by the City to the owner of the abutting lands
In short, many of the provisions specify "provided suitable signs are erected and maintained;", and many others do not, often within the same sub-section. I could quote many more examples. There appears to be no general rule that signs are required, it depends on the particular text of the particular provision. I do not know if the courts enforce these bylaws as written, but if there is a general rule requiring a proper sign, it is vary odd that some provisions specify a sign and other adjacent provisions do not. It appears that a sign is not required to make a parking restriction enforceable in Ontario unless a particular provision so specifies.