How HAVA and voting of disabled citizens might effect a close election

"Recount Redux?: What Might Happen in a Close Election" shows the results of some research by Dan Tokaji on Equal Vote Blog. Given that the Help America Vote Act of 2002 is responsible for the electronic voting machines that are meant to allow disabled citizens to vote independently and privately, and given that machine type varies, and that some machines provide paper verification of votes while other machines do not... what happens in the event of a recount?

Tokaji writes:

Could the discrepancy between paper and electronic records really make a difference? In a close enough election, it might. If voting equipment and associated errors were randomly distributed throughout the state, then one would not expect it to matter whether paper or electronic ballot records govern in the event of a recount. Even if 10% of votes are thrown out, it wouldn't affect the election result so long as the errors are random -- that is, so long as they affected all candidates equally.

In reality, however, voting equipment isn't randomly distributed, at least in Ohio.