In Calgary the City sponsors a discounted rain-barrel program every spring which is administered by a charity called Green Calgary (greecalgary.org). The latter uses Plooto for the rebate payment.
I had the same reaction as you. At first I thought it was phishing, then after some research was convinced it was on the up-and-up, but I didn't feel comfortable using them. I opened a ticket with the City to explain how it looks, especially since their website mentioned almost none of it.