If no mods are made to the mag, and the mag has been approved for import into Canada, it dosen't matter what gun you put it in. The status of the mag or the rifle does not change.
As long as the AIA mags can be distinguished from an M14 mag - no hole should be enough - AIA stampings would be better, and like the AR pistol mag, a paragraph of explanation on the mag body would be even better yet.
The law is very clear on the status of mags, and there is even an added paragraph in referance to "Lee Enfield" mags, stating a legal capacity as 10 rds.
CFC and the RCMP knew the AR pistol mag would fit the AR rifle and they allowed it to be imported anyway. Perhaps they are aware that AIA mags can fit M14s. Perhaps they don't see it as a big deal and are wondering why it took us so long to figure it out.
Do we have the AIAs in .223 or 5.56 here in Canada? If not, perhaps they don't import it here because the mags are exact knockoffs of the AK and AR15 mags. I guess they could still be imported, if that was the case, but the mags would be 5rds.
We still need a report on whether the mag will function, unmodified in an M14.