Think of Airline tickets... from almost the beginning of international flights you could book on one airline for transport that included "legs" on another airline... this continued into the early days of batch computer systems, through the days of online but non networked systems through to today's richly interconnected network systems.

Think of international credit and debit card systems. Travel virtually anywhere and you can use your card from home. Richly interconnected systems, virtually completely interoperable but certainly not from one vendor.

In my mind a one vendor "solution" when the "right" way of doing things has yet to be determined is a recipe for hardening of the system ... if it happens through government fiat (or bribe) look for it to lead to lock-in to unworkable systems that are almost impossible to change .... this can be the only result if "standardization" comes as a result of single vendor lock-in.