Slightly inaccurate
The engineers won't be summoned by the FBI and placed under legal duress. Apple as a company will be the one receiving the order.
If after exhausting their legal options to resist, Apple executives still refuse to give an order down the chain of command to produce a custom build, they'll be held in contempt. If they do give such an order, and the engineers refuse, the engineers can expect to be disciplined and fired. If Apple refuses to discipline and fire them, treating it as a matter of conscience, those executives can expect to be held in contempt again for failing to make a genuine effort to comply.
And the next order will be for the iOS source code and signing key, so the FBI can make it themselves, rendering the entire attempt of resistance moot and leading to a worse outcome all round. As it should be. Nobody can think themselves above the law, and punishment for contempt exists for just that reason.
Biting the hand that feeds IT
