The old CableCard standard was one way only. The newer 'MCard' and the OCAP / Tru2Way boxes are much more capable, and [speaking from the inside of the cable industry] a bit puzzling to deal with.
We are looking at revamping our entire provisioning infrastructure to permit the new generation boxes to function, but that has run into some comical snags. For example, we can't get a Pannasonic Tru2Way set delivered to our lab, because the distributor will only ship to areas served by a Tru2Way compatible cable provider. We're working on it, but we're not fully compatible.