The usefulness of DocWagon is really dependent on the campaign. In a heavy "black trench coat" game it might end up being a way to track a character. In other campaigns it may be that if you give them a half-ass decent fake SIN, or maybe even no SIN at all, they simply don't care as long as you pay the bill. Speak to your GM about how he sees them. The big downside is that they don't violate extraterritoriality. There are still plenty of places where they are darned useful, like being hip deep in the barrens with one health box left and a bike that was overhauled by a grenade launcher strike, I would be heading to the nearest rooftop and hitting the call button.