I haven't found any use for the expensive engineers, anyone know how many resources you get from a scavenged tank as mine have always died whilst trying it. And you can't build with them... 450 manpower is a big investment unless you're getting something concrete out of them.
Have allways thought that they were pretty good so just did a quick test,and was surprised at how good they are:
PIV MP 150+ F 50+
STUG MP 175+ F 50+
AMBULANCE MU 150+
HT MU 85+
T4 MP 120+ F 30+
Its all dependant on how much 'health' the wreck has.
Not sure it helps in a 2v2 but in a 4v4 with a high vehicle attrition its a must!