Just a thought but could the civil war be able to carry over into High Rock?

Nords have always had a presence in High Rock throughout history and even founded some of the cities there (such as Daggerfall - which strangely echoes Dublin of Ireland with the Vikings) and Bretons have assimilated many settled Nordic families into their hierarchy. In early history it was Nord raiding parties attacking the Breton's Elven slavers that discovered them and Nordic armies have contributed to ridding High Rock of Elven oppression in the past. Nords and Bretons share control of the Reach, which though not the best bit of history, they do both share a hatred for the Forsworn and their immoral practices.

Talos's birth is honored and celebrated in parts of high Rock as much as it is in Skyrim. Under the name Hjalti Early-beard it is believed among Bretons that Talos was raised in the High Rock region of Alcaire and they have celebrations and parties there to honor that fact.

Is it possible then that when the Imperials imposed and allowed the Thalmor to ban Talos worship that many in High Rock could have been as put out as the Nords. Is it possible that the Thalmor have taken Breton family members for Talos worship in High Rock like they have done in Skyrim? When Ulfric Stormcloak rose up against the Imperials is it therefore possible that some Bretons could have shared his views and pledged their support to his cause?

Possibly, but the traditional Breton pantheon doesn't put much emphasis on Talos. He's not really one of their more important spirits.