Labial to Dental sound change question

[AnTeallach]

Not quite f → θ, but according to Zompist's numbers page, the Vanuatu languages Sakao and Shark Bay both "changed bilabials to dentals before front vowels", including proto-Vanuatu *vati becoming Shark Bay tharr (which I presume starts with [ð]).

http://www.zompist.com/families.htm

[Qwynegold]

Sorry for bumping in, but could a sound change like {pʲ bʲ} > {tʷ dʷ} happen?