If you are sure they replaced all the rubber, I would take it back to them. If you have damaged something during the year, or have some bad parts, you might need that checked.

I have heard that some silicone spray will quiet the offending joint. Apply and exercise front end until the squeaking goes away. Do not use greases or oils that will degrade the rubber joints or bushings.

I have the same creaking, but I am on the front side of that front end job, not the back side like you!

__________________
Peter
1985 300TD 4-speed 212K
1992 400E 343K
2001 E320 72K