The 8830 WE offered by Sprint is a SIM-unlocked device, you can use any open market (even pre-pay/ contract less) GSM SIM card in Asia/ Europe. But, remember BB email/ browser/ BBM/ BB Maps won't work without a BIS/ BES. Third party apps (like opera mini, gmail app) would work fine on the generic connection. The TOUR 9630 from Sprint is also SIM-unlocked device. (Head to sprint website and find out for yourself: Sprint - Define Region click full feature list )
The 8830 WE or TOUR 9630 or Storm 9530 or Storm 9550 (Storm2) from Verizon is a SIM-locked device. If you unlock it with the specific code it would work with GSM SIM card.
Now, here's the catch- 8830 WE supports GSM in Asian/ Europen bands (900/ 1800 MHz). In the US, T-mobile uses 1900 MHz & AT&T uses 850/ 1900 MHz network. So, your 8830 WE even if unlocked (in case of sprint it is unlocked by default), won't work with T-mobile USA or AT&T. You can use 9630/ 9530/ 9550 with US GSM operators, because these 3 models support Quad-band GSM (850/ 1900/ 900/ 1800 MHz).