By the definition, 75% seems very good. I'm not sure if that definition is a legally sanctioned term or if your municipality has some screwy definition of 'recovered'. But if it really translates to "If this service didn't exist, we would 4x our production of plastic" - then that does not seem like a scam at all.
With that definition, a plausible extreme is they take 75% of waste plastic to create one single plastic cup. Meaning the production of plastic would not change if this program did not exist. If that's the case - then yes scam.
TL;DR not enough info