Ok, now it makes more sense. You have TCAS units that were installed as part of an STC. The STC calls for the TCAS unit by part number. The AD requires SB compliance on the unit that will roll the part number to one not listed on the STC. A repair station authorized to perform the AD/SB does the work and returns the unit to you with an 8130-3 return to servicee. Since the part number no longer matches the STC, you have no authorization to install the new part number unit.
First thing, have you made comments to the Federal Register with your concerns yet? You have until 2/11/2011 to make comments. FAA will have to answer those comments prior to issuing the AD, and there is where you will get your final answer.
When you make your comments, be sure to be clear and concise on your discription of the problem. Identify additional costs that are not in the NPRM that will be required to comply. They only used 2 hours @ $85 an hour. As I see it, you have to remove the unit, ship it to the facility that can make the repairs, recieve it back into your quality system, then re-install it in the aircraft at a minimum. f additional engineering is required for the STC, there are more costs associated with that. You also have down time and lost revenue.
Another concern I have is that the NPRM states "Traffic Alert and Collision Avoidance System (TCAS) units with the part numbers (P/Ns) specified in the ACSS service bulletins identified in Table 1 of this AD". I've never seen an AD that references a vendor document to identify the units that are impacted by the AD. This makes no sense, unless the aircraft operator has the SB, he won't know that the AD impacts him. The AD should identify by part number exactly what units are impacted by the AD.
All in all, this is one of the worst proposed ADs in terms of understanding the requirements.
BY ALL MEANS, SUBMITT COMMENTS TO THIS NPRM!!!!