A Catalan scholar writes: (edited)

I am 95% certain that this is not a folk song but just a 19th or early 20th century parlour song. I can find nothing like it in any of my sources, which are not inconsiderable. Of course, we do not have the tune, and it may be that a trad. tune was used with composed words. I agree with one of the other correspondents to this thread, who casts doubts on the song being folk because of the nostalgic reference to Montjuïc, which historically has been used by the Spanish for bombarding the citizens of Barcelona. The only song I know that refers to Montjuïc is a very vulgar song called "La Ramona i en Tonet" which only mentions the place as somewhere where courting couples do what comes naturally in the bushes. And it's nothing like the song in question.

HTH

Dave