Q&A

So tough to have this happen.
Some repair shops try to lure customers in with a cheap quote for a timing belt replacement by quoting only the cost to replace the timing belt and no associated parts, inevitably once they start doing the work they may call and tell and tell you need to replace many more parts and the cost is twice what you were initially quoted.
Most shops and particularly dealerships do not want "come backs" or try to absolutely cover their liability. For long term durability say a timing belt as a maintenance item should be changed at say 100,000 miles. If you only replace the timing belt you do not expect to be in there again to replace the timing belt say until 200,000. If you are only replacing the timing belt at 100,000 miles you are expecting the other timing belt related components to last until 200,000 miles. If say a camshaft oil seal or crank shaft seal fails at 120,000 miles you are back into removing all the components you had removed to replace the timing belt initially to get access to the seal. Point being any thing that has lasted 100,000 miles and has not been replaced is now expected to last until 200,000 miles so it is a false economy not to replace items that you have removed to replace the timing belt the first time. Many shops on this Subaru will strongly recommend replacing the cam shaft seals (X2), the crankshaft seal, tensioner ,idler bearing, idler sprocket, and water pump.
Its tough the dealer will naturally decline responsibility. If you can prove the tensioner failed because they installed it incorrectly or had over torqued hardware/broke the bolt then they have liability.
If you have the old engine have an independent insurance assessor look at the engine, show him receipts for the work done and see if you have grounds for a small claims court suit. If you have a digital camera and could send me some pictures I will contact you off line and give you my email address.

As a matter of due diligence and also for the sake of component life, I always change the tensioner.. Look at it as wearing a great suit and old, worn ugly shoes. Some things are just not right... Sorry for the damage to your engine.

sounds like they didn't replace the timing belt at all... the forester has an interferance engine meanining if the the belt breaks, it cause the pistons to lock up and the engine siezes, the tensioner should have been replaced at the same time as the belt because they end up taking off the tensioner, 3 different idelers, the water pump, bypass, and thermostat gasket.... All these parts are typically replaced at the same time to save some money in the long run, sounds to me like they either did a shitty job replacing the belt, or they lied to you, sorry for your loss,