Some coaches may have toilets but being able to use them is another matter. The only time I have been able to use a coach toilet was when I went to the USA. Think its a case of the drivers not wanting to clean them out or not having the right facilities to do so. On my last holiday the excuse was that the toilet was of Chinese manufacture and they didn't have the compatible cleaning equipment to clean it.
Avocet
How strange, I would of thought most toilets are pretty much the same when I came to cleaning them. I can understand them not wanting to, but if someone is desparte they should be able to use the loo.
I have only used one so far, that was in Egypt, and came close when I done a Canadian tour, but made it back to hotel in time.