"So, it is possible that he was sent to this company to recover from his wounds?
Maybe - due to his wounds - he was sent to "light duty" untill recovered enough to go back to the frontline units?"
Thats very possible Erwin, my thoughts would be by mid december, most of the infantry divisions were desparate for replacements in the rifle companies and the brass would comb through rear echelon units for qualified personal. Your friend being trained as a combat engineer with battle experience fit the bill.
At the time, the 26th ID was resting & regrouping at Metz.
From 26th combat chronicles:
"On 8 November the Division went on the offensive, took Dieuze, 20 November, advanced across the Saar River to Saar Union, and captured it, 2 December, after house-to-house fighting. Reaching Maginot fortifications, 5 December, it regrouped, entering Saareguemines 8 December. Rest at Metz was interrupted by the Von Rundstedt offensive. The Division moved north to Luxembourg, 19-21 December, to take part in the battle of the Ardennes break-through. It attacked at Rambrouch and Grosbous, 22 December, beat off strong German counterattacks, captured Arsdorf on Christmas Day after heavy fighting, attacked toward the Wiltz River, but was forced to withdraw in the face of determined enemy resistance; after regrouping, 5-8 January 1945, it attacked again, reached the Wiltz River, and finally crossed it, 20 January."