Survival rate of transplanted hair into strip scar by FUE?

Hair transplant to the scar generally do not work as you may expect. Your doctor who performed your surgery (who knows you, has examined you, and performed surgery on you) can answer your questions better.  

Scalp scar revision could also be done with other methods such as simple revision and trichophytic closures, but adding FUE grafts to the scar is usually a good final step. It has to do with the type of your scar.  If the scar is not too thick or avascular (not enough blood supply), you can expect a high growth.  There is not study to look into the exact numbers but I believe in the right scar over 80% of transplanted hair should grow.

Hair restoration to scars in hair bearing areas does work. However the results are unpredictable so one option is to do a test patch to judge individual cases.Scalp scars, beard/moustache scars and donor scars from strip hair transplant are all suitable indications. Beard FUE grafts will get the best 'like for like' match in terms of quality for beard/moustache scars however it is likely that more robust 'chubby' strip FUT grafts with fat surrounding the bulb will do better in terms of survival and growth.Thinner, softer and more vascular scars will probably result in better FUE graft growth rates than thicker, rubbery scars.

That's correct. It's quite unpredictable. A small thin scar might have graft survival of 60-80 %. A thicker scar might be well below 50 %.  0 % would be a shock. But the point is well taken: survival is not only reduced in scars but unpredictable.