Hi "Radiopd",
Sorry for the delay as we like to answer questions as quickly as possible.
Yes you may use that USB modem (the "Rocket Stick") along with an external USB wireless router from CradlePoint. This will provide the IP connection needed for wireless IP remote broadcasts. Simply plug in the USB modem to the CradlePoint wireless router then plug the CradlePoint router into your LAN port (RJ45 jack) on the back of your Tieline G3 codec.
There are two versions of the CradlePoint routers. The CradlePoint 350 is USB-only and is the cheapest at only US$145 or so, The CradlePoint 500 accepts the USB modem plus Express lap top air cards as well as some models of smart phones which is quite handy. It costs only about US$199.
Here are links on eBay where you may see a list of each:
CradlePoint 350
http://tinyurl.com/nk2q75CradlePoint 500
http://tinyurl.com/ygk8srxLet us know if you have any more questions!