Also, there should DEFINITELY be an achievement for holding all 11 keys at once.
i.imgur.com/gSd6g.png
I actually picked up all of the keys (except Teal-White Triangle; not interested in waiting in line for the spawn) at in-street locations. Wish I'd remembered to check the auctions before I bought a Mazza'la Gala party pack though; c25k is a lot more than c890 :(
Bought a couple of extra Purple-Red Square keys at Auction on general principle when I realized my foolishness.