We have a BES (4.0 sp1) ~100 users and use Tmobile for almost all of our devices (mixture of 7230's and 7290's).
Only about half of our devices, however, have a voice plan - the others are on a data only plan. Every device, however, whether or not it has a voice plan has a phone number associated with the device for billing purposes, and if you call Tmobile support for anything that is also how they reference the device.
However, the phone number of the device only shows up on the BES if it actually has a voice plan. Is there any way to get the BES to capture the associated phone numbers of the devices that have no voice plan?
Have you looked in the BlackBerry Handheld Configuration Tool? It will give you a report of all your handhelds including device phone number.
I would caution anyone against removing the phone application. Doing so cuts off access to emergency services. Create an IT Policy with Allow Phone = FALSE and put your data-only users in it. This is sufficient to prevent someone from making expensive off-plan voice calls but still allows 911 calls. Yes, they may have a cell phone in addition to the BB but more access to help is better than less.