Sure. Having different IPs definitely helps (this was my original question if IPs will be different or not). The login to Comcast by itself doesn't help.
I believe authentication is usually handled with MAC addresses. I'm not a network engineer, but I've worked under one and professional equipment has a lot of capabilities for identifying & handling cases exactly like these; don't infer all of the network devices are as rudimentary as a WRT54G
MAC address is used in APR protocol and it doesn't go beyond your router/WAP/DHCP server. The only thing that an "external" server sees is the IP address.
