so has there been a sucessful way of locking on tmo 3g roaming while on att, ie: forcing phone to connect to tmo tower while being a att customer.

Edit: I found a way of forcing n900 to pick up 3g on att by connecting to other towers (ie: tmo).

If you have the gsm/3g app install you can just choose 3g and n900 will look only for 3g. It doesnt automatically connect you to a 3g connection due to the n900 not being able to pick up the at&t frequency. So what you do is click on microb browser it will prompt you about roaming data network and other data rate may apply. if you click yes and there is 3g connection with in the area it will automattically connect to 3g and stay on untill you go out of the area in which that tower is being transmitted which in most case i assume is the TMO tower.

WARNING DATA RAOMING RATES WILL APPLY (at least i am sure it would)

edit:

I guess it was a one time deal i cant reproduce results.. bah.. wish i could.