Roman use of Gauls?

Something I noticed with 1.1 was that you don't get any Gallic regional troops until you have a level 3 local barracks in Bononia and Segesta (presumably the same for Patavium and Mediolanium as well). In 1.0 you got levy spearmen with the first tier, and got more as it went on from there.

Now the reason for this is to reflect the Roman government style (according to MAA). I'm not disputing this change, I don't have a problem with it. But I am curious as to whether there's much about how Romans used Gauls. I know Gallic cavalry was used a great deal, but what about other troops? Would a consular army feature any Gallic components in the socii part? Are there any records of Gauls as allied troops in the period?

Would it be appropriate to have Gallic troops forming the garrison in Bononia, Segesta, Patavium and Mediolanium (as "local levies" serving the client ruler - I do the same with Greek troops in Taras/Bononia/Sicily)?

I know that regarding the Cisalpine region, they got their full roman citizenship around 50/49 B.C. So... I think it depends on the reforms. Regarding that Marius reforms were like... 30-40 years before Caesar, I'd say that 'till you get the Marian Reforms, gaul garrisons are ok. After 20 years or so, you can change them with roman troops. Right? I also remember that some of the tribes in this region remained true to Rome during Hannibal's invasion. That's pretty much all I can tell so far.

AFAIK that's A) to keep the Romans from spamming Lugoae and other low-end Celtic infantry B) to keep them from building high enough "local" MICs once they get Homeland governements in there, since by that point the local Celts have "Romanised"...