Ecclesiastical Latin, by which I mean here the Italian Traditional Pronunciation seems to have preserved some characteristics of rustic Roman pronunciation despite the spelling remaining unchanged:
ae - e (attested B.C.) oe - e (not sure when) ti - tsi (5th Century A.D.?)
I believe [v] (or at least [β]) and palatalised 'c' are attested quite early too. The pronunciation of 'm' and 'n' as full consonants could be put down to influence of the spelling, but from what I have read, 'au' was pronounced [o:] at a very early date. So my question is, if Italian Ecclesiastical Latin has preserved the rustic pronunciations of 'ae' and 'oe' without changing the spelling, why is 'au' not pronounced [o:]? Conversely, if 'au' is pronounced as written, why isn't 'ae' or 'oe'?
Ago vobis gratias Valete