Orchestral wind players: how important is it for you to know when your partner should be in unison with you?

I'm not entirely sure what you're asking here, but I'm guessing you're asking how you should know when and how your partner's part corresponds with yours. And to that I say, just read over their part. Even if you're not great at sight reading, you can have them play their part for you, and follow along as they play. Eventually, as you listen to them play their part along with yours, the more and more that you hear it, the more you'll know what to listen for and expect at certain parts.

If you're trying to mimic the other instruments for any section they are in unison, you've already lost the game. You need to be solid on your part without relying on other instruments to hear where the melody (harmony) is going.

If it is an intonation thing, then that needs to be addressed outside of the rehearsal hall/stage.

You should know both parts as well as your own, always.

That's the deal.

Next, you should know all the other wind instrument players parts as well as your music, so you are that much better a 'section' player.

Next, what the other sections are doing.

Orchestral playing is completely about the whole, and not the individual.

Best regards.