Yes, but not like you would like it to work:
1) You will not get 100Mbps, you will probably not get more than a few hundred kbps of true throughput, limited by the upstream bandwidth on the cable modem.
2) While you are sharing a broadcast media and you can snoop what other people are requesting from the internet, you should not be able to see other pc's directly.
I would setup a pc with a ftp directory and setup a login for your friend, forward TCP ports 20 and 21 on your router to forward to that pc. From the other end just point an FTP client to the outside IP of the router/gateway and you should get a login prompt.
Since you can "put" or "get" with FTP you only need to setup one pc to exchange files either direction.
Not as pretty as network neighborhood, but it will get the job done. This also works if you were on different ISP's too.