The only one I could think of would be this:
Code:
Identifier: PopulationOwnReligion
Trigger requirements: character_record
Parameters: logic token, percent
Sample use: PopulationOwnReligion >= 80
Description: Test the factions religion in characters current region
Battle or Strat: Strat
Class: POPULATION_OWN_RELIGION
You would need a Gihbelline character in each region to check it. And the result would be a total number, like "Cremona Gihbelline >= 80%", and not a relative value like "Cremona more Giheblline than Mantua".