Dealing with vendors and customers provides a very good example of the peculiarities of human behavior.
As a project manager, you may feel obliged whenever you do anything for your customer. But when it comes to vendors you perhaps put yourself in a position above them and treat them differently.
Take this example:
In the IT industry we have a software engineering process group (SEPG) and software quality assurance group (SQAG) responsible for ensuring the implementation of Capability Maturity Model Integration (CMMI) processes.
Project teams follow the groups' instructions and do whatever is required to clear an audit. Once the organization clears the audit and receives a certification, no one cares about the processes anymore because of the following reasons:
1. The project team feels unnecessary extra work was pushed on them by the SEPG/SQAG groups and the project team just wanted to be done with it.
2. The project team feels that they are doing a favor to SEPG/SQAG by implementing the processes rolled out by them, and the SEPG/SQAG feels otherwise.
The best way to keep a sustainable process model is to mentor project teams about the importance of processes to their project. This compare to what we do with our client -- we work as a trusted advisor, providing consultation at each step.
When it comes to an internal project we start treating internal teams as a vendor and ask them to do whatever we need, it doesn't matter if it really adds any value to them. My suggestion SQAG/SEPG teams is that you shall treat the project teams as your client and act as a trusted advisor to them.
This is the only way you can have a sustainable model.