I think it should be possible, but the problem is how you get the tuner card connected with the phone? I mean the phone got no PCI slot or a USB connector which supports host mode on the hardware side.
In my opinion the only possibility to get TV on it is per streaming, except you know a possibility to make the USB connector host mode compatible :P
This is my first post. so forgive me on any wrong doings.
Can there be any application for N900 to make it work as a dream box.
http://en.wikipedia.org/wiki/Dreambox