Direct from the PAL course book
Rimfire rifles have no magazine limitations, providing the magazine used was intended for a rifle.
ALSO
Exceptions
Under Canadian law it’s not what firearm the magazine is used in but what firearm the magazine was designed for, that determines legal capacity. For example, the 10 round capacity magazine designed for the RRA LAR-15 pistol is permitted in use in any firearm, including rifles, that accepts AR-15 type magazines. Another example would be the Thureon Defense carbines using 10 round GLOCK handgun magazines. As these magazines were designed specifically for pistols, which have a 10 round legal capacity, it is not relevant that they can be used in other firearm types.
The Smith & Wesson M&P15-22 can legally only hold 10 rounds as the magazine was originally designed for the M&P15-22 handgun. Even though it is a 22 rimfire rifle, the magazine was designed for use in a pistol and therefore is limited to 10 rounds.
The same goes for the factory Ruger 10/22 25 round magazines. These magazines are limited to 10 rounds as they are also for the Ruger Charger pistol. However, after market 10/22 mags such as the Butler Creek models have no such restriction placed on them, as they are not marketed as pistol magazines. This makes them legal to use in both rifles and the Charger pistol.