Are Guest users on Teams able to access a Planner board created by a licensed user?

I'm adding Guest users to a Team to collaborate and want to use Planner with them.

The guest users will all have only personal, free Microsoft accounts.

1. Has anyone done this? 
2. Will it even work?
3. Will notifications work?
4. And where has the Planner UserVoice gone? It gives me a 404!

Thank you!