As has been said, I'm not sure how it's Niantic's fault that people are trespassing onto their property when the stops are on the park. Though as Clankenbeard pointed out, this might be a brute-force way of getting Niantic to actually listen to them (I mean, this is a company that deals with a buggy feature by going "fuck it" and just ripping it out).
The Rogue Wolf said:
So why not sue the people who are doing the actual trespassing?
Oh, right, they don't have super-deep pockets to drain for easy profit.
Sad truth of lawsuits: wealth is more important than liability when choosing who to sue.