Bower in Rails app before bower-rails

Inherited a project that has has a rather sparse .bowerrc file and a .bower.json full of dependencies at its root. There is no bower-rails in the Gemfile and thus no Bower Rake tasks.

I'm tempted just to drop in the bower-rails gem and move along but curious how the previous team might have interacted with Bower without bower-rails?

Also, I assume .bower.json pre-dates Bowerfile? OK to migrate .bower.json -> Bowerfile or is there a reason not to?

Seemingly simple questions but Bower 'just works' so I don't tend to fiddle with it much.