Yeah, it was a BoA debit card (also my checking account card), and I wrote cash on the deposit slip and sent the card up the tube along with the slip to the teller. You might be right that they wouldn't do it if it wasn't a BoA card -- without fees, at least.
That explains it then. To be honest the idea that people actually still bank with the TBTFs never even occurred to me, so I was working from the assumption that anybody using LocalTill would be someone who didn't have a BoA account.