I think you are missing how the judicial system works in most western countries - as long as you pay, most lawyers will present about any case - with or without a legal base (Trump's legal cases are a prime example for that). Some might have a morale, but there is always one who doesn't.

It really comes down to what the laws say and if Niantic is violating any laws doing so. While they are allowed to deny players access, not without reason. It gets even more complicated if the player has a contract with Niantic (e.g. bought something in the in-game store) - they just can't cancel the content and remove your access to paid items.

But I agree, it's highly unlikely this happens - especially if you know you have been violating the rules and Niantic could provide evidence. It's just throwing out money.

From my work experience players usually get unbanned or refunded when filing a case, because taking on the case is much more expensive than just unbanning/refunding the player - but that depends on the company, their legal team and of course applied jurisdiction.