It is indeed true that taxi licenses in Spain are so outrageously expensive that taxi drivers have to take a mortage big enough to buy a house, to pay for it.
There are certain industries in Spain which have legal barriers of entrance, so that it is very difficult for newcomers to get in, such as pharmacies and taxis. Think of it like a mafia.
That said, it has been proved on a TV programme, that a spanish-looking person taking a taxi, the taxi took a short route, and a foreign looking person taking a taxi from the same place to exactly the same destination, the taxi took a much longer and expensive route.
That said, it is my opinion that taxi driver and truck driver as a career has its days counted, in the light of innovations such as self driving cars. Obviously there will be a fierce (and presumably violent) opposition to the introduction of such disruptive technologies, they will lobby as a group (or as a mafia) trying to avoid that overtaking the market, but in the end those technologies will win.
So in the end, it is irrelevant if Uber can or can´t operate now in countries like Spain, because taxi drivers have no future.
The only hope for smart taxi drivers will be to buy a self-driving car and operate it 24hours a day (that is, embrace innovation as opposed to resist it, resistance is futile), while working themselves on something else, or just enjoying life.