ClubLexus - Lexus Forum Discussion - California O2 Sensor Conundrum

Hi Everyone:

I know it's my first post and I know I'm probably going to get the obligatory "search" comments, but the results I got weren't getting me anywhere... I've been driving for 15 years and did lots of work on my own cars and those of friends, but I never dealt with an O2 sensor issue, so I'm no expert as to what's going on.

So, one of my friends has an 06 GS 300 with about 150K miles, well taken care of by the previous owner with good records and blah.

However, here's the facts.

He needs to get his smog checked very soon, but was rejected solely based on the CEL.
His car is throwing P0420 and P0430.
He takes it to 2 stealerships (Glendale Lexus and Longo Lexus), and they tell him that the O2 sensor is a permanent part of the cats, and by CA law it has to be replaced as one piece, and only at a dealership... When a quick Google reveals that they are modular, so I smelled BS and tell him to look up an independent Lexus shop with good Yelp reviews since I live in OC and don't know who's out there.
He takes it to an indie shop and they do/tell him the same thing.

With the preceding in mind:

Is my friend just being taken for a ride, or are O2 sensors really that nightmarish in California?
If it is indeed BS, are there any reputable shops in the SoCal region (he lives closer to Eagle Rock)?

Thanks for everyone's help in advance!