The info regarding that has NEVER been in writing and probably never will be for what's now obvious reasons.

I fix these cars tubes whenever I see one as I know that replacing an engine or even R&Ring a cyl head is no fun on these cars and would prefer to avoid seeing that happen to anyone.

It's a bad situation, no doubt but if anyone reading this who has an earlier S80 with that tube in need of modification, do make sure to fix it ASAP!.

It's very easy to fix the tube (BEFORE damage that is). As mentioned below, just cut off the extra 3" of hanging tubing flush with the subframe and wire-tie the upper area (near the serp belt) to the large wiring harness. Doing those two steps WILL prevent that problem from occuring.

One more thing....be very aware of the front of your car when parking near those cement parking lot stops or curbs (especially if higher than usual). That includes ice in the winter, equally dangerous to that area.