Read this and the "when the train is at the station" similar thread with a wry smile.
When we were working on the line and stood clear to allow a train to pass, it was not uncommon to see the train with a mist spray, so we got well clear if we saw it, not always possible. Direct discharge not only coated the staff on the line but the sides of the coaches, another reason not to lean out of the window.
Using the loo at the station resulted in an unpleasant working environment, to put it politely. We were one of the few workplaces where customers could crap on the floor.
In the days of guards vans, there were no loos, so they would go on a newspaper and throw it out, in a tunnel if there was one. There are tales of people working in the tunnel copping this output. It didn't make working in tunnels any more pleasant.
On the other thread is a query about peeing on the live rail. This happened on a number of occasions in the non-gangwayed 6 facing 6 with opening windows where the temptation to go out of the window to relieve bladder pressure resulted in a nasty injury and probable removal from the gene pool.
I believe all UK trains have retention loos though some heritage lines may not. Certainly in Europe and Asia the very direct discharge is still prevalent, where you can look down and see the track,