Is it worth learning Fusion Compiler if my company still uses ICC2?

Yes, it is worth it. Most teams are slowly moving from ICC2 to Fusion Compiler, so learning it now keeps you ready for that change. The good part is that the flow and the ideas are very close to ICC2, so it does not take long to pick up once you know ICC2 well. Learn it in your own time. It also helps in interviews, where teams like to see that you can work with both.