Of the factors that drive these variations, STRUCTURE is the most obvious.  Typically, IT groups are structured in a number of ways, but the three most common are:

Full IT Service provider
A single IT group with responsibility for all applications, infrastructure, projects and professional services.  This may include elements of outsourcing, but a single IT group is responsible for all IT service in the organisation.

Data Center Services provider
A central provider of infrastructure services is sometimes established to service the needs of either business-based or geographically dispersed IT groups with 'local' responsibility for delivering Services to their end-users.   This sees a 'cascading' model of Services starting from the Data Center which then become 'input' costs for the 'front' facing IT group to bundle with their local functions into the final Business Service Catalogue.

Federated Service provider (common In Universities)
Usually a central IT group responsible for core technology services and enterprise applications, with faculties, colleges and schools carrying local responsibility for specific IT support needs within those entities.

Significant other considerations that affect design and approach are:

MATURITY STAGES - Within these structures are IT groups at different levels of maturity in Service and Financial Management.  ClearCost Consulting provides ClearCost templates and implementation methodologies to suit most IT groups, from those just starting the 'Service' journey through to those well established with ITIL based Service centric management styles.

FINANCIAL DRIVERS - Whether you have to 'charge' for your Services or not, it is vital to know the true cost of all Services you deliver.  But if chargeback (or cost allocation) is a requirement for you, then ClearCost also provides support for setting and monitoring chargeback budgets, developing funding cases and creating Service Level costing packages.  Partial or full Outsourcing also brings financial management demand that ClearCost delivers on.

OWNERSHIP (the politics) - While bringing in ClearCost is obviously a benefit to Service Management aims, it is sometimes the Finance group that drives the decision.  In such cases, Finance typically takes the lead - giving the initiative a decidedly 'financial' flavour.  In other cases where IT is driving the decision, the initiative takes on a strong 'Service centric' flavour.  ClearCost Consulting has vast experience in all combinations, ensuring a balanced result and maximum benefits to all stakeholders through their implementation design, advice and guidance.

Visit clearcostconsulting.com for further information.