I think there is a broadcast somewhere in the NetBIOS name sesolution. You could try setting up tcpdump and sniffing the traffic.
DNS will work fine. If you add an entry for netbios_name.your.domain, ClearOS will try to append your LAN domain to the name it receives for DNS lookup if it does not contain a ".". Probably this will be much easier than sniffing the packet. Also, I think Windoze tries the same trick and adds the "DNS Suffix Search List" value from "ipconfig /all" to the NetBIOS name and tries to resolve that (whether on not you have a "." in the name which leads to some stupid DNS lookups leaking out onto the internet).