MCU Dialout audio flow establishment is slow

I have been using the MCU dialout way together with a B2B call for a while to deal with outbound calls.

One thing I have been observing is that the audio flow establishment seems a bit slow when using BeginDialout. The McuSession is monitored for McuSessionParticipantEndpointAttendanceChanged events. I get the event about 6 seconds after the outbound call is established. This is a bit annoying to have to wait that long before being able to manipulate the participant.

When establishing inbound calls with B2B to the conference, the event arrives immediately after establishment. 

I’m using UCMA 4.0 with Lync 2013 CU2.