MvdV>> The owner of the coax has a monopoly on it.
KE> There is quite a difference between letting competitors using fixed KE> ciruits and competitors mutiplexing on the same signal carrier.
Of course. Doesn't mean it can't be done. Telecom enigineers have over a century experience in using a shared medium by many parties. The technology is called radio and the medium the aether...
And BTW, DSL circuits are not 100% isolated from each other either. Crosstalk is a serious problem with DSL.