Just clarifying a few issues regarding 'Competitions' and 'Tours'.
So when making a Tour, you select (or for the preset Tour's it's already selected) a Country for the Tour to take place in. For example, Australia. When you add in a competition to the Tour template, the Home Grounds are randomly selected from those that are within that touring nation. So for Australia, there is random choice between Adelaide Gardens, Melbourne Oval, SCG and Bradman Oval.
As for Competitions on their own. The home ground is based on the Home Teams Home Ground. The reason that a lot are getting 'Melbourne Oval' is due to what is set in the Identity of the teams playing.
Also another clarification. Someone mentioned about having to play as 'every side' in Competition or not being able to choose one side. This isn't quite true. While you don't out and out select one single team, you have the choice of simulating through any match you don't wish to play. If you want to randomly play one match with another team, that choice is there too, especially if you end up losing along the way with the team you originally wanted to go through with.