I sort of addressed your question already. If you want to know for sure, call those companies and ask to speak with HR. Tell them you're thinking about applying there for a job and ask them if they're a non-profit and if they are the ones that sign the paychecks for physicians or if someone else does.
Usually organizations that are non-profit are pretty explicit about it in the "about us" portion of their website.
Unless you're lucky enough to run into an attending here who works for those groups and has submitted documentation for PSLF tracking (and thus knows with certainty), no one can tell you for sure--so calling HR is your best bet. As I said above, many non-profit hospitals use for-profit physicians groups to employ their physicians, in which case those attendings would not be eligible for PSLF.