What happens to my Bridging Open Work Permit if my permanent residence application is refused?

The BOWP is granted specifically because you have a pending permanent residence application. If that PR application is ultimately refused, the basis for the bridging permit ends, and you cannot continue to rely on it indefinitely. You would need another lawful basis to stay and work in Canada, such as a new employer-specific work permit or another valid status. Because of this dependency, it is important to keep your PR application strong and your temporary status valid throughout.