Interesting. Although, lest we forget, the Fatah-controlled PA has very little to say about whether Hamas militants go before an international court. Not only do they not control Gaza (where the criminals would be), they are, to reiterate, pretty mortal enemies with Hamas. It's tempting to view this conflict monolithically, but there are factions, and Fatah and Hamas are nearly as opposed to each other as each are to Israel. So this is more a case of killing two birds with one stone for Fatah than it is a brave stand of principle.
There's also the fact that no international body will ever indict a Palestinian rocket man. So it's cost-free along that axis as well.