Shortly after 0900 hrs., a "radio tech" was testing on TGID 7101. A reply from an unknown user stated "loud and clear from the 567.". If he was referring to a "location", this is possibly from 567 W. Lake St. which is CTA Headquarters or just using sequential numbers? Something to monitor for the future.
The Department of Water Management was conducting a safety drill today, possibly at their headquarters which was on Pershing Road. TGID's 4001 (previously heard the Filtration Plants on), 4002 (Self-identified as Security-1), 4019 (Self-Identified as B-2) were in use.
Security-1 originally was in Phase 2, then someone must have turned on a Phase-1 radio which reverted the talk group to Phase-1. TGID 4001 was in Phase-1, TGID 4019 was in Phase-2.
Testing also heard on TGID 4018 from the Jardine Filtration Plant on Ohio, and a second user was at the end of Navy Pier. Not sure what to make of all is today, other than some new RID's were scene during the safety drill. 41573xx, 41574xx series were in use at times.