That's a cosmically trivial distance. Yes we could absolutely detect vast amounts of transmissions at that range, and even figure out how to decode a lot of them. For example video transmissions clearly have a tabular data structure, pixel data structure, timing encoding, serial frames, etc. Theres no way they could be natural. You could even see differences over time as video standards evolve and update. That's just one example. Bear in mind in wartime we manage to extract useful meaningful data from deliberately obscured and encrypted data, so determining useful data from vast ranges and quantities of non-encrypted transmissions would be comparatively easy.