I found this posting:

http://mail-index.netbsd.org/port-alpha/1999/12/24/0003.html

which seems to reflect what I am seeing. Is the data in that posting 
still valid ? (I will try it anyway)

Ok, I tried. It works but I don't know why.

(stty 115200 crtscts clocal; sleep 120) </dev/tty01 &

works and then I can use chat etc. But even after this command exits I 
can still use chat! As opposed to running it without a separate process 
(stty -f ...) when it did not. The magic sauce was:

(stty 115200 crtscts clocal; sleep 2) </dev/ttyXX

thereafter it works (the settings operate and are retained). The 
commands:

stty -f /dev/ttyXX 115200 crtscts clocal

etc, did not have the same effect.

thanks,
Peter