You are harboring a misconception about the architecture of this setup. In particular, console.log in the browser (e.g Firefox) has nothing to do with console.log in the test-runner (Node) as evidenced by the screen-shot below. The fact that you are running in a browser environment is indeed relevant, as you might have suspected.
I'm not very experienced with BusterJS or Node, but in order to have all console.log output appear in the shell, you will need to run the tests in the node environment. This poses an obstacle because you need a Node module to take care of the DOM and other common dependencies such as jQuery.
var config = module.exports;
config["Interval Buttons"] = {
environment: 'node',
};