For quite some time, there have been users complaining of DVB-T scanning problems using application such as MythTV or w_scan. Even stranger, they claimed that using /usr/bin/scan would indeed work as expected.
For example, this Launchpad ticket has tracked the issue for almost two years:
MythTV has a ticket tracking the issue too (although closed due to it being declared "upstream"):
I finally got my hands on some hardware to test with, and what...