Adrian and Chloe O'Brian then left the station on a westbound Circle line train before Jack Bauer was able to apprehend them. They triggered the emergency brake before it could reach the next station, and escaped into the tunnels.("Day 9: 8:00pm-9:00pm")
Although the Circle line does serve Liverpool Street station in real life, the trains used on that line are of a significantly different design from the Jubilee line train that Adrian and Chloe actually boarded. The discrepancy occurred because the scene was filmed on a disused Jubilee line platform at Charing Cross, which was used earlier in Day 9: 1:00pm-2:00pm as a stand-in for the Northern line platforms at both Waterloo Station and Charing Cross Station.