In this scenario, devices on either end of the Palo Alto Networks VWire can send traffic with any tag (Trunk).
To allow specific VLAN tags, add that tag number under 'allowed tags' in Vwire. For a trunk to be passed through, allow all tags '0-4094'. [Network>Virtual Wires>Click on desired Vwire > Tag Allowed >Type in 0-4094 to allow trunked traffic.