Normally the bulletins are very precise in the year range applicable. There may be similar issues with other years, but generally the bulletin calls out years with a very specific part changeover that drives the cutoffs. If yours is a 2000 I doubt any dealer would provide the 2001 service on their dime.
Also note, as far as I know, the bulletins in no way reflect whether or not a dealer is obligated to pay for service out of warranty. It's an acknowledgement that an improvement can be made with a new part/service. Safety items may be mandated to be covered, but some bulletins are simply about avoiding certain cleaners, a rattle in the exhaust, a squeak in the brakes, etc...
Check out this thread:
LX 470 Technical Service Bulletins (TSBs)
It appears the 2000 has the immobilizer bulletin listed.
My understanding is that if you can find someone with techstream and the know-how to reprogram, you can add a new remote to the ECU. People that can and are willing to do that seem very few and far between. The dealer will recommend a new ECU and remote set to the tune of $700-1000.
Given my involvement with keys for these cars I've debated trying to figure out and clearly document the process, but I hesitate because there are probably some potential legal issues with that. Being able to program a key would give you easy access to defeating the security system and stealing a car. :/
