Here's another mention of the 280th at the Battle of the Bulge.
http://members.aol.com/_ht_a/dadswar/bulge/index.htm
They are listed here:
Units at Unknown Locations
There are many units that received recognition for participation in the Ardennes-Alsace campaign. This is a list of some of those units so recognized but for which I have yet to determine their geographic location during the Battle of the Bulge. If you have information on these, please let me know.
260th Engineer Combat Battalion
275th Engineer Combat Battalion
280th Engineer Combat Battalion
281st Engineer Combat Battalion
285th Engineer Combat Battalion
286th Engineer Combat Battalion
289th Engineer Combat Battalion
290th Engineer Combat Battalion
293rd Engineer Combat Battalion
294th Engineer Combat Battalion
297th Engineer Combat Battalion
298th Engineer Combat Battalion
301st Engineer Combat Battalion
303rd Engineer Combat Battalion
304th Engineer Combat Battalion
305th Engineer Combat Battalion
Proud Daughter of Walter (Monday) Poniedzialek
540th Engineer Combat Regiment, 2833rd Bn, H&S Co, 4th Platoon
There's "No Bridge Too Far"