I thing, frequency 5480 IS NOT illegal in most countries (specially in EU). Allowed frequency band starting at 5470, and frequency bandwidth 802.11a is 20MHz, so 5480 is absolutly legal.
official document from Czech Telecommunication Office: http://www.ctu.cz/164/download/VOR/VOR- ... 005-34.pdf
In czech is 5.4 band WIDELY USED, one missing channel very restrict us.
apparently this frequency is illegal in your country for public use. if you have a special license for it - contact support to get a special RouterOS key that unlocks these frequencies. if you think that the list is wrong - send support an official document that proves that 5Ghz is publicly available in your country