So let me get this straight? They're going to place six UHD services on one DVB-T (not DVB-T2) using h.264 compression?
Even using DVB-T at its most fragile (64 QAM, COFDM = 8K, GI=1/32 & FEC = 7/8 that gives a net bit rate of 31.668 Mbps, meaning that slotting six UHD video streams into there will give them an average bitrate of less than 5 Mbps each - that's barely enough for decent 1080i/p video at that bitrate using h.264 compression, let alone scaling that up to UHD.
Unless there'a already a large base of receivers/televisions that can already deal with UHD MPEG4/h.264 DTT reception in Spain, surely a better idea would be to adopt DVB-T2 for the multiplex & use either HEVC or even the newer VVC codec (though I don't think VVC is in use for broadcasting anywhere right now, whereas HEVC has been adopted) for video compression. Time will tell.