That's not to say the brainwave information doesn't contain any useful data. It can be used to detect autism, epilipsy, or other abnormal thought patterns. It's a low frequency waveform, a low humming vibration which can be useful for meditation. Listening to your refrigerator hum can also be used for meditation. It can be used to feedback responses in brain detection systems, to control things. But this requires:
1) A human brain (not included on Voyager)
2) Detection software (also not included).
For an alien civilization to find any pattern in the brainwaves (um .. *toke* .. yeah), it would require a reference database of (human) brain signal inferences to compare it to. Something we don't have ourselves. But consider the variables .. where the sensors were placed, the shape of the subject's head, recording equipment, resolution quality, etc. all color or distort the information.
An hour's worth of humming noise without any meaning or message is all the data will ever be.
If the alien civilization wanted to understand the data, they would need a human brain to study. Which is an invitation for alien invaders to harvest humans for medical study like lab rats ... or to eat for lunch. I will blame Carl Sagan if this happens: