The behavior of a piston experiencing quasi-connectivity and being updated by redstone dust in the vicinity seems to be inconsistent, varying with location. 

In the attached clip, you can see two identical devices using quasi-connectivity, one's piston retracts while the other's piston stays extended. Despite being built the same way, both devices consistently experienced the same divergent behaviors. 

Earlier tests appeared to consistently show that whether devices of the same construction in the same direction remained extended or retracted depended on the parity of the sum of the coordinates, yet the leftmost device shown in the clip (whose activation was not included due to memory limits on attachements) had the same parity as the rightmost device, but instead stayed extended.