Complex sentence: MillenniumIT systems are used by ICAP, the London Metal Exchange, and a series of emerging market exchanges and depositories and have been deployed at the American Stock Exchange and the Boston Stock Exchange.
Split into simpler sentences: MillenniumIT systems are used by a number exchanges and financial companies including ICAP, the London Metal Exchange, and a series of emerging market exchanges and depositories. They have also been deployed at the American Stock Exchange and the Boston Stock Exchange.