Mobile network operators typically want to deal with a single supplier for their major purchases. This allows them to have a single point of contact in case of any issues, such as interworking problems, upgrade plans as well as financial and delivery aspects.
For example, the entire Radio Access Network, including basestations, transmission and cellsite controllers, is often procured from one or two major vendors.
In the femtocell industry, it is common for a single vendor to be selected to provide the commercial end-to-end solution. The vendor would provide a fully pre-tested and interoperable solution either from their own in-house products or from a number of individual product vendors.
Huawei typically provide most of their own equipment in-house, while NEC source many of the components from best of breed independent vendors.
There are relatively few end-to-end femtocell solution vendors today, but these are usually the first point of contact for operators wanting to launch commercial services.