We made the decision to change the tests three years ago, one reason being that even though the tests were still valid and reliable, they dated from 1984-1985 or thereabouts. The way language is used in the government has changed since then. For example, on the written test, obviously the use of electronic mail has changed a lot of things. The style of language has also changed: it is less formal now. There is also the whole language of technology, and so on.
Because of that, the tests had to be modernized and we had to be sure we had tests that were as valid and reliable as possible, based on the best testing practices that apply today.