The Songtradr press release says "we have acquired Bandcamp" - which to my ears sounds like "we have taken ownership of the company registration" (in UK terms). In which case TUPE would apply, if they were Bandcamp employees. Even if Bandcamp was dissolved as a company, I suspect there would be a case for TUPE seeing as the acquisition happened so soon after the dissolution.
If they were Epic, not Bandcamp, employees then Songtradr would be within their rights to proceed as they have. But Epic would have had to go through a redundancy process (including explaining why it's happening, detailing the alternative tactics they have explored and trying to find other roles within the organisation for the affected employees).
Of course, it's all immaterial as UK law doesn't apply (and I only took a short qualification in it so I know it's fiendishly complex anyway).
EDITED to remove information I had included in the original post