Silencers are generally more difficult to self-import, I've heard of problems and delays in getting them through, just because the real silencer (ie, any object capable of suppressing the sound produced by a firearm, replica or not) is ILLEGAL in Canada and thus cannot be imported. However, often enough, airsoft silencers, which are in fact toys, usually get through if the CBSA look at it.
That being said, the relative risk of seizure isn't as high as say if you try to import a lower metal receiver, but of course with any airsoft replicated stuff, the risk is there.
My advice? Get your other stuff from ebaybanned, they are fine, but look to a retailer (I know airsoftparts.ca is a UNCompany retailer in Canada) to get your silencer if you aren't 100% sure on getting it yourself.