Does true supply chain collaboration exist?

to some extent yes.

in large sized,multinational companies there is a practice the operation is optimized to the fullest.

 in our Arab world,i still haven't seen a perfect system yet,but hope in the near future.

yes it do exists but in very limited companies like P&G

Yes , but not widely used in developing countries 

The short quick answer YES, true supply chain collaboration exists in the car manufacturing industry as it is of utmost importance to the success of the industry, since they industry became assemblers rather than pure manufacturers.

In order for the industry to practice JIT and Lean principles they have to collaborate in order reduce or mitigate risk. in their supply chains

Being a part of a big 3PL team with an MNC, I haven't experienced it anywhere despite the best efforts put in objectively by stakeholders. The supply chain is a large entity involving different organizations and we are basically still struggling with the cross-functional harmony within an organization. although organizations are working with data models interconnected with EDIs for real time frontend and backend information flow but the decision making based on this data is slow which stalls the overall working of a supply chain.    

A  certain   organization   should    consider  the  old  school  theory  so that   they   can  feel  the  presence of true collaboration  of  supply chain as  follows:

1. Collaborate in areas where you have a solid footing

2. Turn win-lose situations into win-win opportunities with the right benefit-sharing model

3. Select partners based on capability, strategic goals, and value potential

4. Invest in the right infrastructure and people

5. Establish a robust, joint performance-management system

6. Collaborate for the long term

yes i do believe it exists, simply because no "chain" can be made unless collaboration strongly exists