Bass on power plant lakes will spawn every full moon if the water temps get down in the lower 70's. They also will spawn a lot deeper than a regular lake because they don't need the warmth of the sun.
Not sure on the water temp portion of this but I can tell that I witnessed in 3 straight years on Monti a Summer time spawn way up North in July. It was when the main lake temps would be in the upper 90's to low 100's. The fish would migrate way North where the temps would be closer to 90. We always thought it was just the fish chasing the shad that were trying to find cooler temps but then we saw a ton of bass fry a few weeks after.
To the OP, when Monti was a power plant lake, I always considered pre-spawn late October - mid to late December then the spawn from late December - early March. Ahhh...the good ole days.