The fire truck is definitely spraying water not foam, I doubt qantas would want a double engine change!
Initially the firedepartment used foam, more precisely an AR-AFFF foam (alcohol-resistant film forming fluoroprotein), after that they switched to plain water. (Look at the pictures, the brown stuff being sprayed by the monitor on the crashtender is water mixed with 3% of AR-AFFF.
So that engine definately needs a good look at since AFFF causes corrosion.