As I said in my introductory remarks, customs officials can do many things under Canadian law. Under Canadian law, cell phones are treated like property. As such they can be searched without cause at this time. That is the statute law.
The policy of the Canadian government and of CBSA is to restrict this legal authority such that the devices in question can be searched only if the Canadian customs official has cause to suspect something related to an offence.
So the policy is not as permissive as the law, in my opinion, because the government and CBSA sense that the courts would not uphold the use of powers without cause as the statute law allows.