If the "Welcome aboard" is notable for Dershowitz you should probably note my post next to it.
Alan was "welcomed aboard." Q when talking to Maggie says:
Handler (Conductor):
Smoking can be bad for your health. Read the warning label. Deboard train and walk away. Once in the tunnel, there is no going back.
If Dershowitz working with Q means he is onboard the train then this statement from Q is likely words from the perspective of her handler warning her not to board the train?
Was Q actually showing Maggie that they know what she was told when she considered boarding the train?
What is "the tunnel"?
Is this "the break"?