Generally if it's related to the project and any marketing efforts you make to promote the film, I think "they" will find lawyers telling them they won't have much of a case against you in court because that is the purpose of a release.
However, if you drop their clip into another film or use it in a non-film project, it'll depend on the exact wording of the release you drew up for them to sign.
I think within reason you can do what you want. If you're intending to develop scenes that could be highly negative for their image, then I'd tread cautiously (eg. If it involves nudity etc).