Abu-Abdillah Shu`la, in his book صفوة الراسخ في علم المنسوخ والناسخ, pages 133-135, discusses this claim but does not vote on it. Two of the opinions he referenced are diametrically opposed!
- Judge Shurayh ibn Al-Haarith agreed with the majority that testimony regarding a will of a Muslim by two non-Muslims witnesses to it is accepted. But while the majority have said that the acceptance is contingent upon inability of the decadent to find two Muslim witnesses at the time he made his will, Shurayh has ruled that this condition is unnecessary because the verse is general.
- Abu-haneefa, Maalik and Ash-Shaafi`i have all ruled that the testimony of a non-Muslim in a matter of the will of a Muslim is never accepted.
Shu`la mentions an interesting interpretation by An-Nahhaas: he says that الشهادة mentioned in the verse could mean presence, not testimony. That is certainly valid in Arabic.