Nope, it's a more sophisticated algorithm they're using. Our company held all the patents for locating GSM cell phones calling 911 using UTDOA. The U is uplink, meaning the network of receivers listens when the phone talks. The patents entail each receiver taking a sample of the signal they heard in that time slot on that frequency. They upload the sample to a processor which tries to correlate all the samples with some DSP math, sliding them around in time to see if they match. If they do correlate, the offsets of each one is your delay for doing trilateration.

So if you have multiple talkers at the same time, they can probably be subtracted out by the correlation step.