Can you flip Tideturner on Battlefield B to switch it with something on Battlefield A when someone is attacking Battlefield A?

Ruling: Yes, you can flip Tideturner on Battlefield B and switch it with something on Battlefield A, even when someone is attacking Battlefield A.

Nuances:

• Tideturner's ability can be activated across different battlefields
• Similarly, Zhonyas can be activated on Battlefield A to save a card on Battlefield B (when flipped, Zhonyas is recalled to your base)