Re: Presumbly the UK has similar plans
The Coronavirus Act 2020 was ready to go suspiciously quickly - I suspect there are boilerplates.
It was being implemented before reaching Royal Assent ie before it became law.
For even faster responses we don't really need any additional 'orders'. Instructing the armed forces to assist the police to 'keep the Queen's peace' has been done before in parts of the UK. Not having a pesky written constitution (sorry, Constitution) makes it easier to do.