I am a Seasonal CM and was a CP, and I would like to shed some light on the process for removing trains from the Epcot Beam.
Monorail Pink would be "deadheaded" at Concourse, meaning the Pilot announces that the train is going out of service and must be fully unloaded. The pilot walks through the train to ensure this, then closes the doors and goes back to Cab 1 (normal driving cab for Epcot.) At this point the conversation goes similar to this:
"Central, Monorail Pink is deadheaded at Concourse."
"10-4, Normal Visual to Pylon 30, hold at notify Central"
Pink then continues out in forward to Pylon 30, which places the end of his train (Cab 6) just past the switch point to take trains from Epcot to Express. Once Pink gets to 30 and notifies Central, Central radios shop to move "Switches 8 and 9 to the Spur Line, with power." This is where something went wrong last night. Either Shop didnt comply, Central didn't call, or something malfunctioned. Either way, something went wrong at this point last night.
Central will also call Purple and say
"Monorail Purple you are Normal Visual [if you have a green MAPO and no visual obstructions ahead, go ahead] to Pylon 379, hold and notify."
Pylon 379 is the primary holdpoint for Concourse, meaning if a train is at the station, the train behind will stop at Pylon 379. Pylon 379 is right over the handicapped parking, by the way.
Last night, from what I have been told by people who had radios on them (and switching is really the only interesting thing going on at 2am) that Pink was "Clear to use MAPO Override, in reverse, through 9, through 8, THROUGH BASE, through Poly, through Grand Flo to the Magic Kingdom, switch ends" meaning, had the switches been aligned properly, Pink would have been expecting to reverse COMPLETELY through Base on Express and all the way to the MK. "CLEAR" from Central means you GO. Even if you get an MBS, you MAPO override. Clear is as good as gold, when given from Central.
By this point, Purple has reached 379 and notified so. Central will then say "Purple you are normal visual to pylon 385 [directly above the tram station] then MAPO Override to reach Concourse, hold and notify."
Purple has to MAPO Override because, had the switches been aligned to the spur, there would have been a gap ahead of Purple, which would have given an RED MBS, even though Purple only needed to reach Concourse.
So IN MY OPINION, last night Pink was coming in Reverse in MAPO Override (as required to pass over a switch) but instead of being on the Spur Line, was in fact still on Epcot beam. I do not know why the Pilot did not realize this, but that is not for me to debate. At the same time, Purple was MAPO Overriding from pylon 385. The pilots did not realize their RED MBS was not from a switch being open, but in fact due to the other train. So Pink came through Concourse at 15mph in reverse (as restricted by computers) as Purple was approaching Concourse in forward, in MAPO Override, just past pylon 385 (as indicated by the photos showing it past the tram loading area) and this is where the collision I believe occured.
I have tried to be as factual about the switching process as I can without being too confusing, and the last paragraph was pure speculation, although I feel I have some credence as I took trains to shop nearly every night. Either way, it is a tragedy that a Cast Member was killed, and I can't imagine what the other driver must be feeling, as well as everyone else involved.