I spent a whole lot of time on the phone with Motorola today. If you need to RSD your phone all the small carriers that sell the Milestone X2 use the same SBF. The only difference is the carrier settings which are done at the local store, so if you need those codes or how to do it, call or go by your local carrier.
So, just to recap: The Milestone X2 SBF (2.3.5, 2.3.6) is the same for all carriers.
The reason most people could call but not use data after they flashed the SBF (2.3.5, 2.3.6) is because the voice service WILL work in your home area, but not roaming, until the carrier settings have been programed. Data will NEVER work until the carrier settings have been programed.
I hope this helps!