Diesel engines are a big deal at the moment due to Euro emission standards. Individually, a car manufacturer can't afford to go it alone as the development costs are too high.
At first we were surprised that Ford chose the PSA engine tbh. They were already using the tdi engine in the Ford Galaxy - the Ford Galaxy was a rebadged VW Sharran.
Floor pans is another the manufacturers share. They are jolly expensive to press out due to the cost and size of the dies.
Then PSA use Fiat as their large van supplier with PSA supplying most of the engines - bar the 2.3. Fiat use PSA for their Scudo.
Toyota are now using PSA for their latest van, the Toyota Proace; same van as the Scudo, Despatch, Expert.
The Citroen C1, Peugeot 107 and Toyota Aygo are basically the same car with cosmetic changes all built in the Czech Republic.
http://www.telegraph.co.uk/motoring/first-drives/2735736/Deja-vu-on-a-shoestring.htmlAnd now Mercedes are using the base Doblo as their small van.
There was talk of Fiat selling their whole vehicle manufacturing company to VW about a year ago. Fiat were only going to keep Ferrari. Fiat shares went up 20% and VW shares fell by 20%.

If that did happen sometime in the future, that would have to send major ripples through the industry. Would the Scudo then be sourced from VW and become a rebadged Transporter with a Fiat badge and Tdi motor? Would VW Fiat continue to supply PSA with Relays and Boxers?