I did experiment with this on the N900:
http://www.youtube.com/watch?v=9NCji7j-h5Q

But it required a lot of work and the N900 isn't really powerful enough to decode most MPEG2 streams in software. Here in the Netherlands DVB-T has relatively low bandwidth streams (so it works somewhat), other countries use much higher bandwidth transmission, and the N900 can't handle that.

DVB-H is a bit more complicated. It is available in a lot less countries and often uses encryption (tide to the sim-card). If there is free-to-view DVB-H in your country you can probably get it to work.
Somebody got it to work on a N800 for example:
http://talk.maemo.org/showthread.php?t=17704