Well if it just evolved this ability that suggests it found a unique niche. But it probably hasn't optimized this, since it doesn't have any pressure to compete against other organisms for the radiation source.

But the good news is that we could selectively breed the fungus, or even generically engineer it (once the genes are isolated) to maximize the ability much faster.

I don't know how useful it would be for site cleanup but it might at least become good insulation (like the idea of space station shielding mentioned in the article).