1. Create the file you want to load into the value as plain text and scp it to your destination server.
2. Create an applescript with the following text:
set the text_file to open for access file “Remote HD:path:to:file”
set text_of_file to read text_file
do shell script “niutil -createprop -t radmind/network /computer_lists/Peds\ Managed\ Classic mcx_settingss ‘” & text_of_file & “‘”
3. Save the applescript local, then scp it to the destination server
4. ssh to the destination server as root and run `osascript name_of_applescript`
5. Check with NetInfo Manager to see how things went.
It’s recommended to make the property you add to a non-critical one, then rename it later (example, mine uses mcx_settingss instead of the real mcx_settings value).
Your milage may vary, playing with NetInfo may make your machine very sick and unable to boot. You have been warned.