I know this is slightly off subject - but when you said "Such systems are still working today, decades later. Do you hear of tees failing in carbon steel steam piping? The code is overly conservative and highly specified with no benefit over the designs of decades ago" - please have a look at the pictures on the links below.

There was a major incident at BP Grangemouth in Scotland a few years ago [unfortunately one of a sequence of major incidents in a very short time it has to be said..] An 18" steam main, running in a trench beside a public road suffered
"a catastrophic failure .........(in) a section of the MP steam pipeline. The failure, which occurred suddenly and without warning, involved the rupture of a tee-piece on a 450mm (18” diameter) section of line operating at a pressure of 14 barg (200 psi). Failure occurred in a horizontal section of pipework..... immediately before the isolation valves........... The failure resulted in an “open end” to the MP steam supply..."

Have a look at these pictures from the HSE report into it

http://www.hse.gov.uk/comah/bpgrange/incident/figure11.htm [rupture photo]
http://www.hse.gov.uk/comah/bpgrange/incident/figure12.htm [steam main photo]
http://www.hse.gov.uk/comah/bpgrange/incident/figure13.htm [rupture photo]

It's scary how the tee has been ripped open. The cause was put down to condensation induced water hammer. Failures occur for many reasons, not all of them accountable in the design analysis.