@Anders,
You can't write down an asset that does not exist. Let's look at the last 10-Q.
Cash 5,955
Prepaids 2,262
propery, plant, equipment 157
construction in progress 1,541
right of way 4,236
other assets 755
That's all the assets on the balance sheet. Cash and prepaids are real money, so can't write those down. Right of way is a lease issue, so not specific to the trial.
So they might be able to write down PPE, Construction in Progress, and whatever is in Other Assets. That's a bit over $2 million.
As far as the $1B you mention as spent, that is already shown on the Balance Sheet as $895 million Accumulated Defecit. It has already been expensed, so there is nothing to write off.