I'm in the industry, so I have a little more background on this. They spent about 40M GBP building the system, and it's only been used for two years. It was (entirely?) outsourced to Accenture. Other reasons why the system sucks: It can only handle about 10,000 orders/second, and has latency numbers that are incredibly high (5 milliseconds+).
Looking at other exchanges, there are trading platforms that have been able to last 10+ years while scaling quite well.
TradElect was/is a project management and technical disaster.