And separated by a 4 track mainline that sees trains every 4 to 15 minutes for much of the day.
Oh, and no direct connection. Trains have to run all the way to Gardiner (past Park Lawn) before changing directions.
When GO runs over to grab equipment at the TMC, it takes them 20 minutes just to get there - so at least a 40 minute round trip. Plus factoring in the 20-ish minutes to get to, through, and back from the wash. And the trains still need to be fueled, have the insides cleaned and restocked. Considering a lot of the trains are only at the TMC for a couple of hours, there just really isn't much time to send them over to get washed at Willowbrook.
Dan