Can I be assured all providers on the site are not "LE"?

I think you stand a better chance of TER providers not being LE, but there's no 100% way to guarantee it. There are several posts on the  Legal board concerning this. Don't know if they'll answer your question or give you a warm & fuzzy.
jhb

a problem like that.

Do always follow protocols and you should be fine.

If they have a website and reviews by multiple posters who each have many reviews going back several years, its highly unlikely.

There have been some queries around here about established providers working with LE as part of a deal, but I find that doubtful as well.  It would destroy the providers reputation, and LE wouldn't be likely to get more than a few people before the info got on the web.  It would be more likely that she was feeding the police tips about others on the supply end.

I would be interested in any hard info regarding this sort of thing.