It depends greatly on finer details of the swarm and the coexisting species.
I think other users have put very good points on the psychology aspect of the problem so I'll focus on the material aspect.
Physiology
If the swarm requires a complex network of pipes, fibers or other conduits to keep its member in a cohesive collective and stay sapient, it is quite unlikely that said network will be hospitable to foreign species. Similarly, audio/visual communication used by the swarm may simply be intolerable to others. Imagine a billion insects whining and blinking in a large building where every surface is covered by layers upon layers of droning insects.
Infrastructure
Architectures designed for a species is unlikely accessible to another of great physiological differences. Doors may be too small, mass transport may be inefficient (a 2m high bus with only two decks is horrifyingly inefficient for a species of 20cm tall insectoids), insects that can walk on walls are unlikely to build footpaths that are safe for humanoids, pheromone-marked signs cannot be understood by other species etc. And how about utilities? Species that are efficient at recycling water do not need sewage systems as large as humans' ones to remove liquid waste, while lighting for nocturnal species most likely will not satisfy the need of diurnal ones.
Assuming that the two species are willing to and capable of cooperation, there are still too many factors that may prevent full blending. Of course, these are entirely dependent on your description of the species, and without further details we can only speculate.