I am Australian so I am not familiar with Albertan labour law but I have done a little research and the underlying common law principles are similar.
I will assume that you are covered by Albertan law and not the Canada Labour Code.
The next part of the answer is based on A Guide to Rights and Responsibilities in Alberta Workplaces.
First, if you lost it they would need to ask you to pay for it, they could not deduct it from your pay without a garnishee order (p. 10).
Second, if the device is safety equipment, and it is certainly arguable that it is, then it is the employee's responsibility to use it and the employer's responsibility to keep it in safe working order; this would include replacing it if it were lost (p. 12).
The common law position depends on a) the contract and b) if any negligence were involved.
What does your current employment contract say about your use of the employer's equipment generally and this item in particular? If it says something then, unless it is an illegal term, that is what happens. If it is silent, then it turns on the particular circumstances.
Also, a contract cannot be changed unilaterally, if they are trying to introduce a new term then you have to agree to it; remembering that there may be consequences to taking a stand against your employer, you should say that you do not agree - this removes the risk that the employer could argue that there was tacit agreement.
In order to establish negligence as a Cause of Action under the law of torts, a plaintiff must prove that the defendant:
- had a duty to the plaintiff, as an employee this is virtually a given;
- breached that duty by failing to conform to the required standard of conduct (generally the standard of a reasonable person), this would depend on the circumstances of the loss or damage. You have to take reasonable care of the equipment - this is not a subjective standard, you need to do everything that a person in your position can do to protect the equipment from loss or damage;
- the negligent conduct was, in law, the cause of the harm to the plaintiff. This has to do with the "proximity" of the harm, if for example the device needed a battery change and you took it to a technician who damaged the item in changing the battery then your actions are not proximate to the loss; and
- the plaintiff was, in fact, harmed or damaged. Well, if it is lost or damaged this is pretty unarguable.
So, if you take reasonable care of the device and, notwithstanding, it is lost or damaged then you would not be liable for negligence ... probably.
Talk to your union rep; this is exactly the sort of stuff that they are there to sort out.