Try these expressions for scale and position. You have to hard-code in the initial position of the camera.
// scale
base = thisComp.layer(“Base Layer”); // base layer
cPos = [320,240,-1343.5]; // camera initial position
s = value[0]*length(position,cPos)/length(base.position,cPos);
[s,s,s]
// position
base = thisComp.layer(“Base Layer”); // base layer
cPos = [320,240,-1343.5]; // camera initial position
ratio = length(position,cPos)/length(base.position,cPos);
center = [thisComp.width,thisComp.height]/2;
newXY = ([value[0],value[1]] – center)*ratio + center;
[newXY[0],newXY[1],value[2]]
These may not be exactly right, but something similar should work.
Dan