"Attaching" a trailer to a film means that the trailer in question is added to the film by the studio, not that a given trailer is merely shown in front of a movie. Theaters can choose most of the trailer line-up for a given movie on their own, then
comes a trailer attached by the studio.
If this were to happen, it would not be Disney attaching
a a trailer for a Paramount tentpole to one of their own tentpole films, but the theater deciding that a Trek trailer would be good to show in front of a Star Wars movie.