From my understanding no, that's not the case. IRE is a percentage based value for the video signal being broadcast and since each camera has a different dynamic range the values shown by the IRE will relate to each dynamic range differently. You'd have to do tests with a grey scale (with your shooting camera) to really be able to know how to read the IRE values in stops. This isn't even considering the fact that IRE are logarithmic and not linear so it won't 6 IRE = 1 stop throughout the waveform.