Can, if so how, we sync time via an NTP server in a different domain ?

This is a pure network issue, rather than a Jazz one. If the DEV environment cannot connect to the NTP server in the other domain (or the outside world), there is nothing you can do on the RTC server. You can consider setting up your own NTP server in the DEV environment though.
http://www.borngeek.com/2008/04/03/using-ntp-on-a-private-network/
http://linuxwave.blogspot.com.au/2007/08/setting-up-your-own-ntp-server.html