I'm just going to assume that when you say "authoritative", you mean "valid interpretations of Rabbinic Judaism", and not that it was given to Moshe at Har Sinai or something like that.
From my own experiences, I think that the "average" Orthodox Rabbi probably isn't aware of the Targum Neofiti or of its history, and is thus likely to dismiss it out of hand considering how recently it was discovered (see this answer on the use of unearthed genizah documents or recently revealed manuscripts). While Diez Macho (first publisher of the targum), as quoted on the Wikipedia article, says that it contains "anti-halakhic" material, modern scholars who have studied this targum have found that it seems to fit well with the Rabbinic/Talmudic requirements for being a valid (Orthodox/Rabbinic) translation.
What many people (of those who have heard of 'Targum Neofiti') fail to realize though, is that this exact Targum was actually published under a different name by someone who few would doubt his Orthodox credentials (despite his Zionism): Rabbi Menachem Mendel Kasher. Many volumes of R' Kasher tremendous work, the Torah Shelaima contain a "Targum Yerushalmi", which is the same work that is today referred to as the Targum Neofiti by the scholarly community. The Targum is the main subject of volume 35 of the Torah Shelaima, and volume 24 includes an article by R. Aharon Greenbaum discussing the discovery of this Targum and its importance. (He also mentions the source for its alternative name, though he spells "Neofiti" as ניעאופיטי, unlike the now common ניאופיטי). Besides for these Rabbis, R. Reuvain Margolios mentions this targum in his commentary to Bava Basra 99a (and even believes that this Targum was used by the Rashbam).