The question is debated ad infinitum "If aliens exist where are they?"
One reason why it is claimed that we haven't seen any extraterrestrial radio transmissions is that the supposed aliens are using more advanced communications.
I think this is likely. For instance we have been using radio communication for about 100 years. It is my opinion that this will soon be superceded by more advanced forms such as lasers or something more advanced.
Still I think nascent intelligent civilizations will at least discover radio and will use it for some period of time.
A problem is it's impossible to know how long they would use it. And this report claims detection only out to 1000 light-years. Discussion on sci.astro.seti regards this as extremely optimistic. It might only be 30 ly or so.
So you might have a window of only, say, 100 to 200 years when radio is commonly used, then we might only be able to detect it from stars within 30 to 1,000 ly distant. Taken together these two facts clearly limit the possibilities for detection.

On the question of relevance to this board, if discussion of microbial life on Solar System bodies is allowable, I think detection of more advanced life in other systems should be allowable.
The authors are also published scientists discussing topics they've published on in peer reviewed journals. This particular report has been released to arxiv.org, the physics/astronomy repository, as a prelude to publication.

Bob Clark