This is Liberty from the PagerDuty support team.
If Team A isn’t currently on call during nights and weekends, the quickest way to configure what you’re requesting is by adding Team A’s schedule and Team B’s schedule to the same escalation policy level. This would effectively only notify Team A when they are on call, and Team B when they are on-call, so there isn’t a need to make any schedule edits.
If Team A is currently on call, you’ll want to create a second layer that mimcs Team B’s schedule to make sure that Team A isn’t paged unnecessarily.
Right now there isn’t a way to add a schedule to a schedule layer as a resource, but if you want to email firstname.lastname@example.org, we’re happy to submit a feature request for you. Also, if you need we can look at your specific schedules to make sure that the suggestions I made will actually accomplish the scenario you’ve provided.