Basically, CableCard is broken. Dead Horse, don't go there. Nothing but huge heaps of pain in all directions. The entire standard was designed specifically to skate around FCC ruler-hand-slaps.
Now that we have that established...
You can get the unencrypted channels in the clear using a HDHomeRun. This is a great option, but it only does the unencrypted channels. There are two tuners in the box, and you can get as many of them as you want, just stick them on the network.
For encrypted channels, the only valid option to stream them in-house is to get one of the original Hauppauge PVR cards (PVR 150/250/500/USB2), and connect it to the cable box's SVIDEO and audio ports. This will stream the cable box through the network. You'll also need a USB UIRT per each media director (and at the core) to handle both A/V gear control, and controlling the cable box. If you have multiple cable boxes at the same location, use the GC-100, and connect multiple IR wires (the IR wires you should be using are the Xantech 286 double emitters), to the unit. You'll also need a xantech connecting block (a simple 4 port will do), so that you can control more than two devices. You will also need to create a device template for your cable box, so that LinuxMCE will know how to control it.
For cable boxes at a TV, Direct A/V can then be used, in addition to connecting the cable box to the tuner, connect the DVI/HDMI ports to the local amplifier and to the TV. (remember that I also said a USB UIRT at each station). Now with this, since LinuxMCE would know how to control your TV, amplifier, and cable box (you made a device template for it, remember?), when you switch to Direct A/V, LinuxMCE will switch the inputs appropriately, and any presses on any remotes and orbiters, will go to the right devices in that room.
-Thom