Peter, I respectfully disagree. The program was changed in 1998 or so to remove the trap completely, regardless of condition (plugged or not). All the dealer needs to do is check the VIN to see if has been replaced under the recall yet, if not, they remove the trap & put on a whole new exhaust front to back. If there is any evidence of turbo damage from trap chunks, you also get a free turbo.
The recall campaign (No. 96-1121, updated Feb-97) specifies only that the trap be due for its' next scheduled replacement, which was every 30kmi under the original campaign. I think the only way they would say "no" is if a car currently has a trap with less than 30kmi on it. Otherwise, the campaign specifically states it will be replaced, and that "failure to replace the trap oxidizer as required could cause substantial engine damage."
Of course, things can vary from dealer to dealer depending on their competence, but a phone call to MB USA should clear things up!
Regards,