I put this into the lab real quick with ME-3400E's. On this platform, traffic not matched via vlan mapping command are transmitted unchanged. However, as you stated, 4900M configuration guide clearly states "Packets with unconfigured vlan_ids are dropped."
With that said, it may be possible to implement a workaround by adding a bogus tag and then stripping it. For example:
Traffic from vlan 132 and 133 should leave on the uplink with thier original tags whille vlans 1-5 should have the S-tag of 699. It works in a lab setting for me-3400's. I imagine it will also work on the 4900M.