Actually, the plan for this arctic cable is mostly driven by the needs of the financial-services industry in London and Tokyo (i.e. high frequency trading, ultra low latency direct market access, etc).
HFT is using colo servers sitting as close as possible to the servers actually handling the transactions. No one serious about doing HFT is even considering switching traffic for more than a few miles if they can avoid it. This cable has nothing to do with HFT.
I read that in the article as well, but it didn't make a lot of sense. High Frequency Trading (HFT) typically works in the sub 5 millisecond latency space - and it's not unusual to hear about network engineers who work for financial organizations doing HFT trying to shave off 100 microseconds here or there.
I was under the impression that Japan securities firms were a bit behind in the HFT arena (that could just be a misimpression). Or would this be for foreign branches in Tokyo?
http://en.wikipedia.org/wiki/High-frequency_trading