If they try this in Barcelona, this will only make the growing secession movement stronger.
On September 11 2012, a pro-independence march pulled in a crowd of between 600,000 (according to the Spanish Government), 1.5 million (according to the Guardia Urbana), and 2 million (according to its promoters).
Poll results revealed that half the population of Catalonia (where Barcelona belongs) supported secession from Spain.
I don’t think so. Barcelona is very unionized, particularly through municipal unions, and they are very left wing. Street violence by “workers” has a long history up there.