Another point-of-view from an artist/crafter employed in the giftware industry...
(NOT a fan of CPSIA, not for or against Mattel, just privy to different info than some other people here.)
This isn't some special exemption for Mattel- other companies are moving their testing in-house, they just haven't gotten any press because they don't have a history of recalling their products. The press only mentions Mattel because they know everyone will freak out about it. Watching people freak out is a lot more fun than actually explaining why anything might make sense don't you think?
...generic explanation as to not give out anything classified...
Other companies are also currently working on setting up in-house testing labs. Right now the test fees alone are adding maybe 10% at retail to every item they sell. (it varies.) Moving the testing in-house will allow them to sell the same safe products they already sell for the same prices they used to sell them for, and keep their customers from going ballistic. (Once the set-up is complete. But first it's going to cost a fortune.)
It's better for the company, it's better for the employees of the company who now won't need to be laid off when the company makes up the cost by cutting payroll, it's better for the small retailers who buy product from them, it's better for the end consumer whose dollars aren't going as far these days.
The same rules still apply, regardless of who performs the test.
Approved product that reaches the U.S. market is still subject to inspection, recall and lawsuits.
And unless the CPSC is planning to hold Mattel accountable by testing every single item they import (hard to enforce legally when Mattel was allowed to pay a fine without ever admitting it did anything wrong, and it also wouldn't go over well with taxpayers who would have to fund all the building, equipping and inspecting that would require) it makes more sense to allow the on-site inspections that are part of the deal, that will really speed things up and save $ for the CPSC.
and- there's nothing inherently more reliable about 3rd party testing anyway. Testers are independent business owners operating a business for a profit. subject to all the same error-making, cost-cutting, corner-cutting, and back-room-deal-making that goes on in other businesses. Most are located in other countries & aren't run by American citizens, so legal recourse against them -by injured U.S. consumers or by the U.S gov't- is limited.
If Mattel (or anyone else) was just trying to get away with something, I suspect that it would be a lot more cost-effective to bribe someone at a testing facility than to build your own. And way easier to pass the buck when something goes wrong!