ATR's "Both main hyd pumps loss" checklist calls for closing (or checking closed) hyd crosfeed, so after the landing gear lever is lovered, dc aux pump kicks in and gives you some pressure to lover flaps but gear goes down with a little help from gravity. There's warning in FCOM that in case of go-around you can not retract the gear, therefore it seems to me that opening crosfeed to pressurize green system by using dc pump is not ATR approved procedure, at least for flyers. I couldn't find the reason for it written explicitly in the FCOM but our French instructors told us that DC pump is too weak to supply both hyd systems.