They would see our narrowband carriers. :-)
I was thinking something similar, but we use so much of the broadcast spectrum and, since the Earth would appear to be a point source, I imagine there would be all kinds of overlap of the different bands and frequencies from all the radio sources, as well as possible attenuation from interstellar media. So my first thought is the spectrum would look fairly broad and incoherent in the radio region and then taper off where the spectrum goes to shorter wavelengths. Would there be specific, narrow band emissions that would not overlap?
I suppose so -- and I suppose also that they'd be narrowly focused S-band type signals sent from blowtorches like Goldstone, Madrid, and Canberra.
The question is: how likely is it that one could pick up such signals, even from big, powerful sites like those, at a distances on the order of light years?
I'd think it would be hard enough to detect extremely weak signals sent to us on purpose, much less incidental signals directed to (say) some alien version of Pioneer 10.
Leaving aside questions being batted about in this thread, what's your personal opinion of the likelihood of ever seeing such signals, assuming they were sent?