Using Sindome as an example, I imagine that holidays for corpies would be more about one-upmanship, showing off and making passive-aggressive attacks against one's peers. For mixers they would either be largely ignored as it's hard to care about the new year when you're struggling just to survive (maslow's hierarchy of needs anyone?) or used as an excuse to escape reality for a little while with emphasis put on intense partying, drinking, drug use or similar borderline, self-destructive means of escape.
Either way the festive, good natured, love to the world and self reflective goodness we might be familiar with just doesn't feel right to me in a Cyberpunk setting. In the end though, I don't really have a good point of reference. Could anyone recommend and good books, shows or movies that give a cyberpunk take on holidays?