It's been confirmed that the machine god is the void dragon. Machine spirits are AIs, that's also confirmed.... As for aiding.. as they said, the void dragon is in stasis/torpor, he's being fed massive ammounts of energy by the ad mech which is keeping it passive, meanwhile they manage to glean bits of information from it now and then.
There's no doubt that Emps has some pretty crazy abilities that could be construed as being Omnissiah-esque, but the Void Dragon is definitely the deity that the Mechanicum worships.
Personally, just think that a machine's 'spirit' is any of the logic programming it has/AI, and the Void Dragon is just a really powerful AI
AI would imply that it was artificial. The C'Tan may be beings of energy, but they arn't artificial. remember, the Necrontyr found the energy beings floating around suns, then crated bodies for them. Before this they had very little 'sentience' and were basically just sitting around soaking up energy. Once the Necrontyr coaxed them into bodies, they suddenly had a sense of what all was 'out there', and tastes for more exotic energy, like souls.
I know daemons can be crammed into machines, but I've never heard of that happening with human souls.
There was one case of a techpriest losing his body but being able to travel from machine to machine on contact and control them , much like a demon would , except he aided the Imperium and somehow kept his sanity. It's an extremely rare case though.
