Here's what I've learned so far:
Rebuilt MCE 1.1 only this time I went for broke and installed everything (which meant having a hybrid core/media director). No problems.
The intercom function simply does *not* work not matter what combination of buttons I click.
From the core, I can dial direct to MD#1 from the core and everything works; I can talk to someone sitting at MD#1 through the core. The same intercom loop I mentioned above is still present. For example, click the Intercom button from the core and click MD#1 when asked who you would like to call. At the next screen, you'll be asked where you would like to call from. Choose to "place a call from here" does absolutely nothing. If you choose to place the call from the core, it loops you back to the previous screen asking you whom you'd like to call. Broadcasting to all media directors does nothing but send you to a screen with a clickable button marked "End Broadcast".
If I can directly dial a MD, the intercom should work by contrast.
As for MythTV, it detects my card as HT878. I admit I haven't worked with MythTV very much and I haven't actually researched whether or not this card will even work with MythTV.
I'll keep plugging away.