Hi -
The LDAP integration is done by integrating the UCCM with Active Directory. Here is a good link that discusses the method of authentication - http://www.cisco.com/en/US/docs/voice_ip_comm/meetingplace_express/2_0/english/administration/guide/cm20call.html#wpxref1369283
"Requirements for User Authentication by an External Directory:
You must use Cisco Unified Communications Manager Release 4.0 or a later release to use an external directory to authenticate Cisco Unified MeetingPlace Express users."
I could be wrong, but I thought MPE only integrated with CallManager, whereas MeetingPlace was the product to use with non-UCCM PBX switches. Here is another link that discusses how to import users into MPE -http://www.cisco.com/en/US/docs/voice_ip_comm/meetingplace_express/1_1/english/administration/guide/bagmport.html
Ginger