There’s something quite seriously wrong with the grammar of the whole ST extract, as quoted.

And the upper-case “T” of Técnico is worth noting. It strongly suggests “Técnico” is a noun (and not a mere common-or-garden “noun”, but something approaching a “proper noun”). In any event, it’s not a simple adjective (“técnico”) as suggested elsewhere on this page - and still less a component of the adjective "técnico-económico".

With those thoughts in mind, I suggest that it might refer to a “well-respected economic analyser” who prepared the "volúmenes de esta pre-oferta".

I understand that "Técnico económico" are used as adjectives that modify "estimado". That is to say, the estimate consists of two aspects or components.

I found something similar in this page:
http://www.rwe.com/web/cms/en/1789148/rwe-technology-interna...