So they'd seek a truce a truce with the Ivory Tower-Highfair mafia to buy some time.
If I recall correctly each territory has one Mafia and one Detective faction at work? Or at least is allowed that. So backroom deals between opposing faction could be a thing?
Mafia supports a Detective in taking hold in a territory, and the Detectives willingly turn a blind eye to them unless they're directly impacted?
I like your thinking. It's one faction per territory. So if you attacked a Detective district, that detective would get pushed out. However, you could form an alliance and 'share' a district. That would just mean the resources are split between you. Backroom deals are absolutely encouraged.