Subtitle settings in iTunes content on iOS are wrong
It's possible that the Spanish subs are hardcoded into the movie (i.e. part of the video track, not a separate track). This is often the case for English language films with small portions of foreign languages. My copy of Quantum of Solace (not from iTunes) has some hardcoded subs for Spanish parts around the 28 minute mark (haven't watched the full movie in some time, there may be others).

I'm not sure that would explain why the English subtitle selection doesn't display anything however.