Let's get straight to the point. This is my fictive network architecture:

My question is: Would it be possible for Laptop B to intercept traffic sent and received by Laptop A? Please note that B only has WiFi access and no physical control over Router B. Furthermore, Router A and B create different wireless networks with different encryption keys.

If both shared the same wireless network or Laptop B had LAN-access to Router B, the answer would be trivial, but I'm not sure how the answer turns out in this scenario :-/

Thanks for your valuable help!