In most dialects of Occitan, the letter <u> is pronounced [y] generally. However, in Provençal it appears to be pronounced [œ] by some speakers some of the time.
This wikipedia article states (without a source) that it is a feature of the Rhodanien subdialect in particular.
It doesn't appear to be all words where [y] becomes [œ]. Listening closely to this Provençal example, the <u> in words like 'degun' and 'luna' sound like [œ] to my ear, but in 'un' it is clearly [y].
Is it in fact a feature primarily of Rhodanien, as the wikipedia article states, and what rules govern when it is [y] and when it is [œ]?