Vendors cause IMS implementation hold-ups

In the recent issue of "Telecommunications" Iain Morris wrote that British incumbent BT blames network equipment vendors for hold-ups in IMS implementation.
There is no vendor that provides equipment 100% compatible with the IMS standard. Of course, all the vendors provide "almost-IMS" solutions that work but not interwork.

Malcolm Wardlaw, BT’s director of converged services says

"When vendor equipment meets the standard it will be a lot easier for carriers like BT to mix and match vendors, and that’s critical both commercially and from a resilience point of view,"

And another quote from the article:

According to a new report from consultancy Analysys, that problem could be endemic. "It is difficult to produce a business case for a generic capability like IMS without being specific about the services that it will support, and compelling service propositions have not yet been forthcoming,"

BT strategy is to provide wireless services through partnerships with mobile operators. Lack of IMS-compliance makes this task impossible.
It seems that the two parties (operators and vendors) have different views on the situation.
As we can see, telcos say that vendors are not ready for IMS. Vendors say that most network operators are not ready for IMS — they have no business cases and no well-defined migration strategies.
I'm afraid that almost nobody is really ready for IMS yet. So it is possible that another standard architecture becomes obsolete before it gets implemented.