I don't think so. There's all kinds of polarized radiation sources all over the spectrum in the universe and known to astronomers, from masers (the astronomy ones, but a similar question could be if we could detect high energy emissions of masers of the other kind, that could be used as source of microwave beam-powered propulsion), magnetars splitting and merging x-rays and polarizing its surroundings in the process, and so on. And there's plenty of other naturally occurring astronomical radio sources too, that could easily mask any polarized sources and convert it all into unstructured white noise.
So unless these synchrotron radiation sources exhibit some other distinct and indisputably intelligent design characteristics (i.e. they would be intentionally used to transmit their location, as a sort of a beacon, perhaps repeating a sequence of prime numbers or alike), they could be easily lost to background noise or dismissed as a natural source. To my knowledge, nobody is (currently) explicitly looking at polarized radiation sources with intention of discovering high energy technosignatures.
But since such source radiation would be neither narrow beam nor capable of high bandwidth communications due to its sheer required size stretching several light hours, it wouldn't make much sense to use it as anything else but a beacon anyway. And, as far as we know, we might have already detected just that in the so-called Oh-My-God particles, it would just be a bit of a stretch drawing such vast conclusions from half-vast data, to quote Jerry R. Ehman, the person that discovered the Wow! signal and famously circled the data print-out and wrote Wow! next to it. They might just as well be emissions of a perfectly natural process that we don't yet fully understand.