Is the BPM/SOA approach at its core different from other methodologies that have already been employed to bridge the business-IT gap?
There are several categories of main-stream system development methodologies from traditional-structured (prevailing in the 70s and sometimes called waterfall methods) through object-oriented and iterative methods (developed in 80s and 90s to replace the former) to modern agile modelling (‘configurable’ methods targeting the project needs) and extreme programming technics. The methodology metamodel aimed to provide an open standard for defining any (business or IT) system development methodology can be found here.
The common characteristic of all system development methodologies is that they are deeply rooted in the IT side of the spectrum and have typically evolved from modelling static and dynamic aspects of programming code and data structures. Therefore, even after being extended to address the needs of business modelling and analysis they do not resonate well with business community and none of them has been widely accepted for the purpose.