Unfortunately, the message protocol is completely flawed security-wise, which allows malicious actors to control the power station.
It would require only a handful of strategically placed senders to control an estimated 20 gigawatt of load Germany-wide, causing havoc on the European energy grid (brown-out, cascading effects, etc.).
The security researchers followed a responsible disclosure towards the vendor, EFR, who reacted with sending letters from their lawyers.
Today's SPIEGEL online news magazine pre-talk report ( https://archive.is/p66as ) on this topic cites EFR that the proposed attack vector is not possible.
The security researchers therefore made the last minute decision to go full disclosure with today's talk to press on the urgency of the topic.