And that's assuming you are only talking about one species on competition with itself. You have different animals all squished together with different but overlapping needs and you have an ecosystem to work with. Werewolves probably would tend to a territorial pack hierarchy, but there could be several packs near each other if they have reason enough. Vampire may be all Victorian Court style, or just as easily fit a solitary hunter motif, or rodent like sewer goblin. But were the wolves may naturally form into packs, maybe vampires are solitary predators (the Cats to the wolves Dog). Maybe the Lizard People in that are mistaken for sewer alligators can have a more complex society since they stay out of new tunnels and thus the human eye most of the time.
One good thing to look at is the "peace" of organized crime. Its some of the most Darwinian corners of society around, and shows how a bunch of widely diverse groups can coexist. It depends on the "business" of each, and in a fantasy setting you just have to look at it with monster needs in mind. Mobs in a city tend to stake out territory in terms of geography and/or product. Street gangs that do intimidation rackets and the petty crime stuff, but may not get into drugs or gambling or prostitution. Likewise the drug dealers probably don't care who is robbing jewelry stores, as long as they Mind Their Own Business. You could well have ecosystem like that. Maybe Werewolf packs are the thugs, and each have a neighborhood, and brawl like you'd expect. Meanwhile the Vampires run the drugs, but have a truce with the wolves in exchange for Red Cross Blood Drives (which goes to hell when the next Alpha steps up). Maybe there is a small school of Sirens out by Pier 13, but they don't really bother anyone else, and sometimes will distract border patrols for friendly smugglers. Arms dealers could probably care less whats happening on the streets, unless that is their market.
One of those things with UF you have to think about is what force is keeping the supernatural out of the public eye. Is it a Masquerade, some conspiracy between all supernatural factions, and if so what made them all agree to get along? Is it the combination of technological disruption and subconscious human disbelief that keeps humans from noticing? Is there a secret government cover-up, some Men in Black agency that swoops in to invalidate and steal the camera footage? Personally I'm a fan of the Fall of the Black Court; the idea that one of the superpowers was nearly annihilated by what from their perspective amounts to a horde of chickens, and all the rest are afraid it will happen again.
But Oz makes a good point. Sometimes all it takes is simple food supply. Running with that thought, it doesn't make natural sense for predators to compress and cooperate in any degree in a city like that. Rather they would either consolidate the city as a single, particularly bountiful territory, or else they would go out into the wilderness to get the isolated prey that has not concentrated itself for herd protection. But in the modern age, as society has developed and communication has become so ever present, it would have reversed the situation: in small rural areas, Taken Prey would make much more of a stir than in a crowded city where the prey are killing each other every day. Survival would push them to enter the cities and blend in, the proverbial Wolf in Sheeples clothing. That would probably chaff the longer lived of the supernatural predators, imitating their prey instead of maintaining the pride of yada-yada...
Anyways, many ways to take it, depends on what you want it to do for you
