The US operators have been engaged in a string of 5G-focused spectrum auctions, large and small, since the incentive auction of 600 MHz broadcast airwaves in 2017. There have been three millimeter wave sales, which attracted limited interest, plus three sales in the all-important midband spectrum, which AT&T and Verizon have lacked in the first years of 5G roll-out. That shortage severely limited their ability to offer the same strong balance of capacity and coverage that T-Mobile has achieved with its significant investment in 600 MHz licences, plus the huge swathe of 2.5 GHz assets it acquired with Sprint. The auction of CBRS priority access licences, followed by the showstopping C-band sale – which cost MNOs $95bn – and the…