My cat has tape worms. How can I get rid of them?

I had him treated by the vet last summer with a pill they gave him and following up with the Frontline flea treatment for months afterward. It didn't appear to work as I still saw another one shortly after treatment. Tonight a lot (several)of the worms are coming out wheras the 3 times I've seen it before it was only 1 or 2. I intend to have him treated by the vet again. But I live in a house where there are several other cats belonging to three other people, all but one are outdoor cats and of course are going to bring in fleas. If I keep my cat indoors all the time and treated for fleas after the vet treats the worms, won't the other cats bringing in fleas make the treatment worthless as they are still fleas in the house to be ingested? It's my stepdad's house, one other owner is a renter in the room next to mine, and I'll be renting a room with my son who is due in December so I can't make everyone else treat and contain their cats and treat the house and yard. It'd be impossible.