I dont know where you live, or what logistics are involved in getting from shul to the train. in my neighborhood the 5:50 minyan ends early enough to first stop for breakfast at the bagel store with time to get to the platform by 6:50.
To answer your questions.
A-was it possible they davened early enough for a 650am train
It is possible.
B-would they get to the manhatten with enough time to catch a minyan
Depends. Where are they leaving from? what minyan are they trying to make?
C-do most bachurim on bein hazmanim continue going to minyan the way they did during zman
Lets put it this way. The retirees in my neighborhood cant wait for bein hazmanim, it is when the shteeble has a 9:00 weekday shachris as well 🙂