Thank goodness we don't have that problem here. Especially when delivering downtown, the cops here are pretty cool. There are precious few unloading zones, so some streets are designated that we can park down the middle, straddling the double-yellow line (delivery trucks only) and some streets are designated that we can take stop in the right-hand lane, so long as we keep our hazard lights on. Sometimes a rookie takes offense, and goes to issue a ticket for it, but all it takes is a phone-call to the PD and he's on his merry way, no ticket.
I think it all comes down to the fact that our management team struck a deal with the local chamber of commerce: if we cannot legally park within a certain distance of any given business, then that business can come pick up their own stuff at the center (otherwise we would be pushing a cart all day making 1/4 and 1/2 mile trips to and from the truck - we couldn't have that.) Needless to say, the chamber heard that and immediately pressured the PD into relaxing the parking standards downtown.
That's what all the old dogs tell me, anyway.