Hi Rico,
I’ve done a design review of another LA firms work as requested by their Client. This is a common practice and the objective is not only to review but also to have an outsiders view on the project. We also do this internally at EDAW with our Creative Review process where other members outside the project team analyze and critique the design during the different stages of the project.
In reviewing other firms design, you have to know the design brief and this will be your basis in giving an objective review. As you’ve said, there should be respect and in no way that you should attempt to supplant the other firm to obtain work from the client.