Head-to-head play has been a long requested feature. It was, IIRC, supposed to be in OOTP6 but was scrapped when Markus ran into too many difficulties coding it.
OOTP 2007
does feature the ability for two managers to play directly against each other, but only locally.
In theory, you could use some sort of remote desktop software like
TightVNC (which is freeware) so that you can share the desktop over the internet, although I'm not sure how responsive OOTP would be to such a scenario.