I can speak to that.
The current authorization-to-transport application does have a list of purposes for transport, one of which is temporary storage with an individual or at a business location. The individual or business where it would be temporarily stored has to possess the privilege to possess that class of firearm.
Within the authorization-to-transport regulations, under, I believe, section 1.2, which is “manner of application”, it states “being made in the prescribed form”, and the prescribed form—being the application—is what indicates the temporary storage element. It's not clearly articulated in the regulations, but because it's the prescribed form and the ATT regulations refer to the prescribed form, that purpose of temporary storage is currently in the law.