More than likely replaced in that time. Deptford have had a few allocations on for one run and then have taken them off after one run lately, from what I've noted. I have no idea why - especially in the cases of "Northern" vehicles - but it seems to have happened a few times recently.
As far as I'm aware, the 61 does not interwork with any other services on the morning duties.
RE: Odd Allocations