I have the Toshiba 51H83 and I think they upscale to 1080i if 720p automatically if it isn't selected. All tosh models natively will switch to 720p if that is what the signal produced is (that's why you love Toshiba and Hitachi, 720p natively!) I have owned 3 versions of Toshiba (had an old 43" 1st, then a 46 , now a 51 which is 4 months old.) You can't beat the price/performace vs. $$$$ in any other brand. The picture is superb!
And you are correct. When hitting the Info button on the remote, it never shows what resolution signal it is, just that it is in HDTV mode......
Also, look on page 12 of the manual in the side note (upper right had corner of the page) it shows that the TV will display 480p/720p when connected to the HDTV Colorstream connections.
Hope you are happy with your TV....I know I am (I also got a great deal on mine, it was only boxed on left before the new H/HX84 came out and I got it for $1700Cdn which is about $1380USD, couldn't beat that!)
I've played soul caliber 2 and it looks absolutely amazing running @720p (I'm positve it is @720p, nothing has ever looked that good on my TV other than HDTV sat!)....