Suppliers of large companies jump through hoops for their customer - it's a requirement of doing business with them. So, to do business with GM say, you need access to design information for new models, inventory information ect, - you need to access their network. When GM adopts the SEP model, the supplier will be required to own TPM-enabled machines and register with GM's ERAS. This forces the supplier to own, operate and manage their own SEPs. The supplier, in turn, finds this to be an excellent business model. It rapidly gets adopted throughout the industry as a Good Manufacturing Practice (GMP).
You say, 'not likely'. Well, every supplier today who enters any manufacturing facility as a qualified vendor is required to do site-specific safety training, carry large insurance umbrellas, demonstrate adherence to GMPs and regulatory compliance. The new 'compliance' is rapidly becoming secure access and secure data.
This will also be particularly true of first tier DoD vendors, who will in turn, push the model to second and third tier suppliers.
Game - Set - Match.