SCO Group sued AutoZone (full text of the complaint) for having used their libraries when they migrated to Linux. They don't have any evidence, but rather just say "they did it too fast, so they must have gotten help from IBM and stolen our code". (Note, it didn't have anything to do with the Linux code).
The lead developer at AutoZone at the time of the migration writes on Groklaw that the SCO claims is a pile of %$%#$.
They also sued Daimler Chrysler, but it's not entirely clear that has anything to do with Linux either.