Telus is a CDMA network. CDMA does not use SIM cards. GSM uses SIM cards and the only Canadian company that uses GSM (so far) is Rogers. However, Telus is going to become the first (in Canada at least) GSM/CDMA network. This will happen in about 5 years, they are going to do that for another 5 years than drop CDMA once they have enough support. They will start dropping CDMA by ending sales of it, and they will also start turning off towers slowly. Eventually (very very long time) they will be all GSM. You can expect Bell Canada to follow suit, just a year or 2 behind.
Telus has 3 networks: Telus Mike(TDMA), Telus 3G(CDMA), and Telus 4G(HSPA). The Telus Mike and Telus 4G networks use SIM technology.
Since Telus Mike is TDMA(a precursor of GSM), it has a much more limited international coverage area. Outside of Canada, you can use it on some networks in the US, Argentina, Brazil, Mexico & Peru. You'll need to ask Telus which carriers they roam with since they don't have that information readily available.
Telus doesn't have any intention of phasing out it's CDMA and TDMA network anytime soon. A large part of their user base are large corporations who use the networks for data acquisition. Telus could lose a lot of revenue if it forced these clients to upgrade to HSPA before it is economically feasible for them to upgrade communications.