There is a tshuva from Rav Moishe Feinstein ZT”L in his Igros where he addresses this issue and comes to the conclusion that if a certain havara is being used by a major portion of Klal Yisroel, it has a din of Lashon Hakodesh for everyone, and thus, a Sefardi could be yotzei from an ashkanazi and vice-versa.
His ra’aya is from Chalitza which has to be said, al pi din, in Loshen Hakodesh. Now, supposing the woman’s normal havara is Galiciana, while her deceased husband’s brother’s havara is Litvish- does that mean that the Chalitza is invalid because the woman’s havara is not Lashon Hakodesh to the man and vice-versa? No one has ever heard of such a psak. So, concludes Rav Moishe, this is proof that all havaros and dialects that are being used in Klal Yisroel have a din of Lashon Hakodesh, and one could be yotzei Krias Hatorah from someone with a different havora.