A large component and service-based software system exists in different forms, as different variants targeting different business needs and users. This kind of systems is provided as a set of "independent" products and not as a "single whole". Developers use ad hoc mechanisms to manage variability. However, for deriving new product variants that are built upon existing ones, the presence of a single model describing the architecture of the whole system with an explicit specification of commonality and variability is of great interest. Indeed, this enables them to see the invariant part of the whole, on top of which new functionality can be built, in addition to the different options they can use. We investigate in this work the use of software product line reverse engineering approaches, and in particular the framework named But4Reuse, for recovering an architecture model that enables us to build a Software Architecture Product Line (SAPL), from a set of software variants. We propose a generic process for recovering an architecture model of such a product line. We have instantiated this process for the OSGi Java framework and experimented it for building the architecture model of Eclipse IDE SPL. The results of this experimentation showed that this process can effectively reconstruct such an architecture model.