This is the result of the language having been made illegal, then not illegal, then taught predominately by the school systems.

Is it possible the 55% who speak Spanish primarily fall along those demographic lines? Is it also possible that some portion of that 55% speaks both Spanish and Catalan?

Sincere question. I know very little of the situation.

I also have a friend who has been teaching English as a Foreign Language in BCN for at least a decade now, and he and his wife tell a similar story.

"In any case I would love to be able to express better myself in English" - you already have a fluent grasp of English. You spelt it's with an apostrophe which is spot on and come across as a native writer - for a given value of "native" 8) Good skills mate.

This is not the same thing. My mother tongue is not my (current) habitual tongue. I don't see where the report shows the habitual tongue spoken.

Llengua o llengües que la persona ha parlat primer a casa seva. Es considera que aquesta llengua ha estat transmesa familiarment i adquirida en el procés de socialització de l'individu.

This is not the habitual language. So, where is it?

http://www.idescat.cat/cat/idescat/publicacions/cataleg/pdfd...

"Initial language" (page 45):

Catalan: 31.6%, Spanish: 55%.

"Identification language" (page 48):

Catalan: 37.2%, Spanish: 46.5%

"Habitual language" (page 51):

Catalan: 35.6%, Spanish: 45.9%

Edit: in my first comment in this thread I spoke from memory. Also, the data from the 2013 poll (official data):

https://www.idescat.cat/cat/idescat/publicacions/cataleg/pdf...

"Initial language" (page 45):

Catalan: 31%, Spanish: 55.1%.

"Identification language" (page 46):

Catalan: 36.4%, Spanish: 47.5%.

"Habitual language" (page 49):

Catalan: 36.3%, Spanish: 50.7%.

EDIT: Seems like that's the old poll. There's a new one from 2013, in which both Catalan and Spanish grew as the habitual languages. It still doesn't reach 55%, though.