It's not that hard
"DAB requires infrastructure beyond most pirates' resources" - yeah right.
Complete DVB-T (FreeView television) output on a PCI card for under £2k (just need to add a PC, software, amplifier and transmission aerial):
Similar DAB cards are also available. I couldn't find a price from a quick Google but they'll be similar. e.g.:
(It's a T-DMB card, but that's a superset of DAB). These cards are intended for people who want to test DAB receivers. You run a cable directly from the card output to the receiver's input, no radio license required.
Presumably the pirates can get amplifiers and aerials already, so what's the hard part again?