Somwhat similar concept to 'HD-MDI', where each camera connects directly to the recorder using CAT5/6, but is not IP surveillance. i.e. images/video are not encoded & compressed (or by any intelligence) on each camera, they are just raw signals sent to the recorder (which then takes care of encoding/compression etc).
Again, this defeats the purpose of using any kind of intellegence at the edge device (camera), as it's with surveillance.
HDBaseT is intended for audio visual use, not surveillance. Though I know at least one company was trying to push their chips or reference designs for surveillance a year or two ago.
It's interesting for things like digital signage where you may be able to run small displays via a single cable. It could also simplify camera control for A/V applications which often still require a separate RS-485/422/232 cable. I don't see it going anywhere for surveillance, though.