If you have a local industry, especially if that industry is struggling due to lack of work, cancelling, delaying or sending contracts off shore is false economy.
In the short term the premium paid for local construction is usually lower than the increased tax receipts from the benefit gained through spending the money locally. Over the long term, ordering as many, if not all, of the ships the navy requires, locally will increase the efficiency and expertise of the local yards, reducing the premium paid for local construction, reduce through life costs for sustainment and increase the critical mass of national project management and heavy engineering skills to the benefit of the economy.
Japan, South Korea and now even China are off shoring commercial work to lower cost countries as their wages, conditions and pollution controls improve and increase costs. The improvement in efficiencies in their shipyards can't compete with the low wages in Vietnam and the Philippines etc. I imagine African nations getting into shipbuilding next.
Simple steel bashing for ships with a limited economic life can be off shored but more complex work is expensive whether done locally or overseas. If you have a local industry it makes sense to give them all of the work in a well planned, sustainable manner, to increase your economies of scale than to waste money on make work projects and rebuilding / revitalizing the industry in between the projects you do retain.
Another factor that comes to mind is currency values, I am not sure but believe Canada, like Australia has had a long period of stable high currency, due mostly to commodity prices and low ( on a global scale) debt. This has made off shoring look more attractive at the same time as making conditions very challenging for local manufacturing and heavy engineering. The failure of government to compensate for global conditions and level the economy means that Canada (and Australia) are particularly vulnerable to dropping commodity prices and when the dollar inevitably drops too the off shore option they are now tied to will be much more expensive, perhaps unaffordably so.