BitLocker management is not supported and does not currently work with IBCM (or a CMG). It's being worked on and will hopefully be added to near future (maybe even the next) production build.
As for MPs on secondary sites, the locator service does not consider them for BitLocker recovery. Clients always require connectivity to an MP in the primary site so this aligns with that basic requirement. Also, escrowing a recovery key is not in any way network intensive and only happens when the key is set or rest so bandwidth usage is minimal and trivial even.
Is this causing you an issue or are you just validating?
If it's causing you an issue, you should file an item on UserVoice.