There isn't barely indication for Nusrah having a support base among the tribal population around al-Bu Kamal city and I believe that they recruited mostly from urban centers.
In the following part, I want to take a closer look at Liwa' Ahl al-Athar, which was the most influental among them:
This gets clear, when looking at their martyrs. There are reports from most villages between Bahrah and al-Bu Kamal, except the 'Ubayd (not part of 'Uqaydat) villages of Abu al-Hasan and Abu al-Khatir.
There is a mention of a killed fighter from Shu'aytat town Gharanij, but it doesn't go any further, neither north nor south of the Euphrates.
It is also mentioned as part of @alasalawatanmya, but this affiliation seems to have been rather loose.
But earlier, in April 2014, Nusra and FSA in Baghuz "besieged" IS cells in Shaykh Hamad village.
In two seperate attacks in ash-Sha'fah and Baghuz, three IS members were killed and over ten wounded.
This are of course doesn't mean all members of a tribe are unitary.