I had a big accident recently and spoke to ICBC about this.
Basically the condition is a moving target based on what's most economical for icbc.
They will give your car a market value dollar amount(actual cash value). If this actual cash value minus the salvage value is lower than the repair cost then its a writeoff.
So lets say your car's actual cash value is $30,000 and they think they can get 17,000 at auction. the difference is $13,000.
If your repair is $7000, your car is repaired. if the repair is $15,000 then it's written off.
Source:
ICBC Write-offs