Damn vistair.... it seriously indicates it as 29-20 controls and indicators overhead panel.
As the Blue system on the A320 (unlike other Airbuses) has no ED pump, robbing the Yellow system of its AC pump can be done to "get you home".
Sure, but the system was designed for the PTU to power the other system in case of an engine shutdown or EDP failure. There is no issue with running the yellow elec pump to makeup for lost EDP output either (PRO-ABN-29 HYD Y ENG 2 PUMP LO
PR (PTU inoperative)).
As such a continuous running PTU is not a danger, as long as there is fluid in the G and Y reservoir.