Hi,
There is a supplementary information regarding TAXI with ENG#2, but only to the A319, the reason is because in Heatrow there are some parking positions where when operating the A319, the Port engine must be shutdown, just because of the distance to jetty.
Airbus states that is acceptable for exceptional cases to have ENG#1 shutdown instead of ENG#2, but one has to ensure that the nose wheel steering reamains available, the green HYD SYS remains pressurized, this is achieved provided the PTU is available (FCOM DSC-29 HYD)
The procedure is the:
APU - Start
Not less than 3 min after reverse operation ENG#1 Shutdown ( in your case is already Shutdown)
Ensure on SD that GREEN SYS is pressurized.
Even this is an special procedure for the A319 you could do this in the remain variations i.e. A320/321 , the system operation is the same.
Of course this not recommended to do on daily basis, just in exceptional cases.