Plumbum,
And you airline folks---- don't forget ----- an aircraft with 1090ES ADS-B Out will only produce the same ACAS/TCAS response as a Mode C transponder equipped aircraft, ---- 'cause you ain't got ADS-B IN to your ACAS/TCAS 11, and are not likely to have it any time soon ---- and even when you do, the results will not be any different.
Thats why UAT and transponder. 1090ES IS a transponder. UAT is just a broadcast of GPS vector...what makes UAT different is the bandwidth available for transmission of FIS-B and TIS-B.........thats the expensive ground station bit...not so much the ground station but what is connected to it to enable the those transmissions. Plus the fact that TIS-B is a position every 12 seconds or more...after all it is from a radar feed. UAT is ground station dependent..ES is not.
And just think --- Airservices could drop a UAT card into the vacant slot in their ground stations and Hey!! Presto!! ---- (relatively) cheap ADS-B.
Does that mean you advocate low level roll-out, Leadsled?