No the file is created by the humax from the contents being written to the time shift buffer irrespective of content (you also get a .nts with a recording which is why recording it and playing back the ongoing recording works).
Done some experimentation and the channels that live pause have a slightly different format.
eg Heart FM (which works)
Format : MPEG Audio
Format version : Version 1
Format profile : Layer 2
Mode : Joint stereo
Mode extension : MS Stereo
Codec ID : 4
Radio 4 (which doesn’t live pause)
Format : MPEG Audio
Format version : Version 1
Format profile : Layer 2
Mode : Joint stereo
Mode extension : Intensity Stereo + MS Stereo
Codec ID : 3
Chances of a software update would seem to be zero especially as a very simple workaround exists.