An almost planet-sized, solar-powered radio transmitter could generate enough energy to propel an interstellar light sail (like the one illustrated above), they suggest. These sails, in turn, might be sufficient to push “about 20 times the largest cruise ships on Earth.” FRBs would be the leakage from such transmitters.
Harvard Scientists Say Aliens May Be Using Giant Radio Beams To Travel The Cosmos – Huffington Post