the closest thing i found to an answer was in the release notes for MBG Release 7.0.15, a lot of the older RN links were error 404 on the mitel site.
5302 Set NOT Supported On MBG
Due to the specific requirement for this set to obtain option 125 from the DHCP server on boot, this set will only boot when connected directly to a 3300 ICP and not via MBG.