Reverse that, FG is a factor of attenuation. Attenuation is determined by wort compostition, yeast strain, and yeast health, nutrition, etc etc. But in the case of FG from 2 identical worts, but with different yeasts, the average attenuation of the strain would be the determining factor in the FG calculation.
Yeast attenuation as I understand it is a factor in FG which is part of the BV calc. Not sure what you are trying to do, can you point me in the right direction.
the BV calculation takes into account the FG, and the FG will vary depending on apparant attenuation (amongst other things)....so, in an example wort, if your using a low attenuator, eg 1469 with average attenuation of only 69%, compared to high attenuator, eg nottingham with 76%, it will effect the FG, which will affect the BV.
This would be a handy thing for those brewers that are using yeasts that have attenuation averages available. Obvioulsy in a kit and bit scenario, the attenuation needs to be skewed in the calculations to take into account the relative fermentability of the individual ingredients. The way I do it is by calculating the percentage of the contribution to gravity of each ingredient...the malt component is assigned the attenuation of the actual yeast, simple fermentables are assigned 92%, and unfermentables are assigned 0.