[DLCPhoto]

Well, I tried it out to see what would happen: changed my TP2 from CDMA Only to GSM, and just tried making a call to Celtrek using their regular 10-digit U.S. phone number. I didn't change Assisted Dialing or anything else. I received the call-back within a few seconds, as I'm supposed to, and I was connected to them without any difficulty at all!! I checked my "Call History" and it seems the "+1" was automatically entered to the 10-digit number!!

So assuming it works like this when I'm out of the country, I should be able to just make calls with my regular contact list, same as usual. As I've said elsewhere, I have no affiliation with Celtrek, but have been quite impressed both with their Customer Service and the fact that everything has worked as promised, without difficulty or unwelcome surprises.