To be honest, I'd been given the full impression that most cabs were fitted with "comfort pipes" to direct fluids into the cess and keep the cab clean. In the case of female drivers using such facilities, I'd imagine that they'd either carry adaptors around with them or they may be stored in the cabs themselves.
As for 2X-- coded jobs though, my advice would be to try and go before starting the shift!
Though I'm no train driver I have to confess that I have found myself in a similar situation to them on one occasion. I was on board the last service of the night from Woking to Waterloo which - Much to my inconvenience (Pun not intended) - Was being run non-stop via the Richmond loop and formed of 2x455s.
Although I tried my very best to avoid having to do so, I was eventually forced to resort to fishing an Evian bottle out of the dustbin, make rather abnormal use of the coupling vestibule, then lob the sealed bottle out of the window into the LuL cess.

Thankfully I was one of only two passengers on board that whole unit, and with the other passenger being a Chav I knew full well that he wouldn't be bothered!
