As I understand it, it works the same as any other explosive. Assuming you've not changed radius calculation parameters, it calculates the explosion radius from the 'power' value and plops down a full-power (well, there seems to be a somewhat variable starting density/time-to-live, too; per tile, even) smoke instance on every tile in the radius. For explosion height, you get an additional malus to vertical radius depending on the 'battleExplosionHeight', or no verticality at all with the vanilla option.
But since you're forking the code, you can (try to) read it yourself. I haven't checked if the above is true code-wise, that's just my understanding from experience and documentation.
