Sorry, it's not something we've tried.
There's some additional info on 3G for CCTV in this thread, maybe if you call one of the 3G specialists mentioned they might be able to offer some help/experience?
3G for CCTV is very unstable due to the fact that video requires a 24/7 video streaming and 3G connection varies a lot depending on movement, quantity of people connecting to same cell, high traffic download from some users, etc