Not sure how to handle PT as a divorced parent?

Tecnically I wasn't married but that was the easiest way to explain it.  I was engaged and now we are split up.

I read Todller 411 about the one day potty training or whatever it is and basically that  was my plan to wait until DS is showing the signs listed in the book.  The book indicates that boys typically aren't ready until close to three years old.

My ex and I are not on speaking terms.  We do not speak at all about anything.  We both have attorneys and I am still trying to get child support and a fixed visitation schedule for his Dad.

However, my DS told me that his Dad's girlfriend bought him underwear and I heard him talking to his Dad on the phone and his Dad asked him if he was going to use the potty chair.  So it sounds like Dad and his girlfriend are already pushing my son to potty train. 

I am so freakin annoyed by this because he isn't even two years old yet.  He will be in two weeks.  I take my son to a Montesorri school a few days a week and they are obviously trained professionals and they have not indicated to me that my son is ready for potty training.  I do not like the fact that my ex is going to be pushing potty training on him when he probably isn't capable of it yet.