I had a rear end collision in my 2013 Fusion, went to a respectable body shop, they fixed.  I asked for the fresh wheel alignment; the rear toe is OUTSIDE of the minimum specs.  The left should be a min of +.05 degrees and mine is -.08.  The right should be min .05 and is .02.  Total rear toe should be min .10 and mine is -.07 degrees.

The body shop and their associates, the alignment shop, say that the car is old and the suspension is rusty, therefore they can't adjust the rear toe, BUT they say that won't be a problem - the specs aren't bad enough to start eating tires.  

The car has always worn tires evenly and properly.  I just recently bought a new set of tires.  Will these specs cause problems for excessive tire wear?  Is it possible that the specs were better before the accident and the body shop didn't straighten the body properly?  The pressure is on to just accept the job (to be fair the car appearance is good), but what happens if in six months my expensive new tires are toast?

Ok all fair questions. 

Firstly assuming this is a uk fusion i think your rear axle is like a fiesta from memory so your rear toe isnt adjustable anyway.

Secondly did you have recent 4 wheel alignment print out prior to your accident? It may have been like this for years but with no symptoms. 

Also 4 wheel alignment can be wrong if it is rushed and gauges not fitted fully snug .

If this is an american fusion then it is fully adjustable.