If I understand you correctly, you are looking for a tool in Vegas that is similar to the motion tracking tool in After Effects so that you can use it to track a mask. Am I correct?
I am not familiar with After Effects so I can’t help you but I just thought I would translate for others. Sometimes it’s very hard to get the right English sentence out doing a literal translation from another language but you’re doing fine. ;-)
What Vegas does have, is the ability to keyframe the movement of a mask using Vegas’ Track Motion. It doesn’t do camera angle matching if After Effects does that but you can move the mask manually with keyframes.