According to Sasktel's wikipedia page Sasktel is now running a UMTS/HSPDA+ network.
Yes, on frequencies not supported by the European Desire HD
Will this phone work on any 3G network in the USA?
No
Ok will the Desire work on the 3g network what about the Nexus One?
The Telus Desire, once unlocked, will work on Bell/Telus/Rogers/Sasktel/AT&T HSPA networks because they all are 850/1900 MHz.
The euro/asian Desire will have the same problem as the euro Desire HD, they are both 900/2100 MHz.
There are again two Nexus One.
One works on the 1700 AWS frequencies (WIND, Videotron, T-mobile USA, etc.), as well as euro/asian 900 and 2100 MHz bands.
The other works on 850/1900 (Bell etc.), as well as 2100 MHz.
So all I have to do is buy a tri band android phone for it to work?
No, you need to look which bands are supported for WCDMA. If it is 900/1700/2100 then you are out of luck on Sasktel.
And I think Verizons network is different as well and wont work in Canada..
Verizon phones are CDMA2000 / EVDO. So they can roam on the old Bell/Telus. But they don't have a SIM card and I don't think they can even be switched to a different carrier.