They wouldn't be ready to be used. They'd be defueled and likely some important components of the power system and weapons are missing; things that are easy to replace but necessary for it to work. They'd also have no interior atmosphere. Vacuum is a much more gentle resting place.
There a various degrees of deactivation. I think the GTVA probably went for something along the lines of a boneyard rather than mothballing. The ships were seriously stripped down before deactivation and lack weapons and other major, expensive, and easily reusable components, but the hulls are still intact and it would be quicker to reactivate them then build new ones.