A friend of mine potty trained her child because of an increase in fees at her daycare. She was in centre care and her son was aging out of one room, and the next room up only allowed potty trained children. So the centre was going to levy a monthly fee on her for the additional hardship on the staff in the new room since they were not supposed to be changing diapers. I know your situation is sort of different but you wouldn't be the only person/caregiver to do this. Her son was turning 3 I think.

Commando style training isn't great for a daycare situation but undies with plastic pants over top or specialty cloth training pants work great. I used them for my own son. You could tell the mom that from now on for potty training pulls up and diapers are not allowed and the child will have to come in waterproof undies. I think that doing the laundry of a poopy underpant rolled up in a shopping bag might prove to be an incentive for her even more than paying extra.. lol. If they bring him in a diaper/pull up in the morning simpily ask them to please change him into his undies for the day.