Take for example the case of cell phones. Many cell phones talk to the same base stations. Once the base station decodes the stronger signals. It can subtract this now known signal allowing for greater signal to noise ratios for the weaker signals. They have been doing this for at least 8 years. Similarly the phones can decode and subtract out higher power signals from the various base stations.
Even the compressed signals are not random. Each symbol will be one point on the possible modulation constellation. Without decoding the signal you can make some pretty good guesses and subtract out strong signals giving you better signal to noise ratio.
In addition to the data signals there is a large amount of non random reference signals that can be removed.