There are two primary components to IT... the design/development of services, and the opertaion/delivery of services.
"Business - IT Development" alignment is driven by business requirements (functional, service level, cost, time-to-market, etc). SOA isn't a "requirement", but a technique that helps IT achieve the desires of the business to support their business processes.
"Business/IT Operations" alignment is properly performed as defined by ITSM/ITIL Best Practices, and as illustrated in my graphic below. Business and IT need to work as a intimate partnership to define, implement, deliver, and continually refine an optimized Service Portfolio at contracted service levels and an established and predictable cost point. Again, SOA is simply a technique that helps IT achieve operational excellence.
All other functions are internal to IT. The fact that requirements are fleshed out in an Agile fashion and constructed/deployed using a SOA strategy is meaningless to the Business Unit. They simply want IT to build the capability they need, adjust it when asked, and deliver it as expected.