As a bus driver, my experience is, the older diesels needed idle time to cool down the turbo and exhaust manifold after driving and to air up when starting, though it really didn't matter how long you idled them, and they idled at far less rpms, being far less noisy.
The newer diesels with the DEF and REGEN do not idle well, they need to be set at a VERY high idle, like they are ready to fly, which is far more noisy. A low idle creates all kinds of issues with the REGEN, filter clogging, turbos issues, etc. Expensive!
People are aware of diesels now because of the high idle rate to work with the pollution control items.
The newer diesels may be more "green" however most consume more fuel and have more issues with the new technology, meaning more down time.
Sad but true, the very reason we went with an older, far more reliable diesel.