I dont think that it is too late to start training him. Although I have never had to Im sure it can be done even at his age. The sooner the better ...
Im wondering who if anyone is home with this little guy during the day?
It will take much much more than just a few trips out doors to get him trained. Plus it is going to take everyone in the home to pitch in and help. I dont see why they wouldn't seeing as how this is their home and they want to prevent it from becoming a doggy waist land.
I have some tips for training on my site that may be helpful. It will probably be much harder than if you were training a pup since he is stuck in his ways but very much worth all of the effort it will take (for everyone) to get this guy potty trained.
Training Tips - Dawn's Yorkies Ohio
Good Luck !