I haven't seen the Russound intercom units in person, but did talk to the Russound employees about it during lunch when I was at training last week.
It looks like it will work well (and will even work with other DA systems), but I was dissapointed in how it actually "integrates".
It works by using a powered keypad (think A-Bus) which connects in the speaker wire between the amp (CAV/CAM, etc) and the speakers. When paging is enabled, the system will basically disrupt the local source using a relay that routes the audio from the intercoms built-in amp to the speakers instead.
Like I said... not the slick integration I was hoping for, but looks like it should work and because of how it connects it will work with other manufacturers systems too.