Has anyone ever done the maths?
The outgoing signal from Arecibo may have been up 30TW EIRP but the transmitter was only 1AU away from a white noise source producing over 100YW EIRP. I dont know what the sig/noise is at whatever frequency they are planning to use but I find it hard to believe it is greater than unity.
Also, even with the best optical telescopes, exoplanets can only be resolved if they are an order of magnitude further than 1AU away from their star. So the chances of someone sitting on an exoplanet being able to resolve a 2GHz(ish) radio signal and block the noise from the sun and filter out the CMB is less than the chance of seeing with the naked eye, a gnat taking a piss while sitting on the horizon at sunset.