Unfortunately this is not a viable proposition for a couple of reasons.
Firstly, the powerline adaptor is expecting to see/drive an Ethernet signal on the cable, when what is will actually see is HDBaseT signalling and protocol. So it will not even be able to establish a link with the HDBaseT equipment (note that if the HDBaseT equipment supports Ethernet fallback mode, then it should be able to establish a link BUT only 100M Ethernet can be carried, not all the HDBaseT traffic).
Secondly, even if a link could be established, HDBaseT operates using an 8Gb/s (spec version 1.0 and 2.0) or 16Gb/s (spec 3.0) asymmetrical link. This far exceeds the bandwidth that the protocols used for powerline communications are capable of (and probably that the copper wiring is capable of). For example, Homeplug AV2 protocol supports a peak speed of 1300Mb/s, meaning that it can run up to 1G Ethernet.
So as I said at the start my answer, unfortunately this is not possible.