Clyde 1 is part of the Freeview radio line-up, according to
http://www.radio-now.co.uk/freeview_radio_epg.htm.
Presumably they've decided it's worth their while to pay for the national coverage.
It makes a nice change from us having London's local stuff foisted on us as if it were of national importance, anyway.
Clyde 1's not a bad station actually, Mrs T usually has it on the radio in the car.