Managed by both AGA and LU according to Wikipedia.
Silent on who manages the toilets though.
On the
DLR▸ Platforms so I'm guessing it's LU... All the signage is in LU Blue anyway
Another reason why toilets at stations need to be kept open is at times of disruption. If you have been kept waiting for 2 or 3 hours with no information, the lack of a toilet could be a major additional stress factor!
Even a 30 minute delay can be an issue. Board a train without a ticket as you couldn't get one but do have the means to pay and an immensely full bladder. What should you do?
Purchase your ticket and then go to the toilet? After all you have to purchase your ticket at the
earliest opportunity
Or do you make a bid for the toilet, then go and buy your ticket and risk the possiblity of awkward questions as to why you "hid" in the loo...?