OK people, most people here are right, and most people here are wrong. Let me explain.
The Blu Win HD and Blu Win Jr. are both dual-SIM phones. They are 3G for the main SIM slot, and 2G for the second SIM slot. This second SIM slot is what creates the confusion. Fido (when they were independent) went GSM for 2G. Rogers when IS-136, but later switched to GSM. Everyone else (Telus, Bell, Sasktel, MTS, TBayTel, you name it) all went CDMA2000. Unlike the American carriers who stubbornly stuck with CDMA2000 through the 3G era, the Canadian CDMA2000 carriers all sensibly abandoned it and switched to HSPA over half-a-decade ago. That means that unlike Rogers, they don't have 2G GSM support.
This means that SIMs on the Rogers network (Rogers, Fido, Chatr, Cityfone, 7-11 Speakout, etc.) will all work in *both* SIM slots. This also means that SIMs on *every other network* in Canada will only work in the main SIM slot. Put your Telus, Bell, etc., SIM in the wrong slot in the Blu Win HD or the Blu Win Jr. and it won't work.
As for the new entrants (Wind, Mobilicity, Eastlink, Videotron, etc.), they also don't have 2G GSM, but instead of HSPA over 850MHz and PCS they're rocking HSPA over AWS. This is a problem for the Blu Win Jr. as it doesn't support AWS. The Blue Win HD comes in two variants, and you'll want the "U" variant which does support AWS. Last I checked you could get this version from some sellers, but Microsoft was unfortunately selling the variant that didn't support AWS.
The new Blu Win HD LTE supports 3G AWS, so ironically (depending on where you're buying it) you may have to get the LTE version to get 3G support over AWS.