The normal setup for the scenario you mention is that your Cisco router would plug into the RG. The RG would provide a private 192.168.200.x address to your router. Your epuipment would then continue to function as it normally would. You could even configure a static private 192.168.200.x (2-19 are reserved on the RG) IP address to your Cisco router from the RG.
I would suggest a static Real World IP address from CBT's network to your equipment. CBT offers a single static IP or 5 static IPs. CBT can configure the RG to use the static route through the RG assigning the Real World IP to your router in your network. This maintains the managability of the device as well as allowing your router to have a static Real World IP address.