Distributed generation and the urge for a more efficient grid operation will increase the frequency of network topology reconfigurations in tomorrow's power grids. High-throughput synchrophasor and intelligent electronic device readings provide unprecedented instrumentation capabilities for generalized state estimation (GSE), which deals with identifying the power system state jointly with its network topology. This task is critically challenged by the complexity scale of a grid interconnection, especially under the detailed GSE model. Upon modifying the original GSE cost by block-sparsity promoting regularizers, a decentralized solver with enhanced circuit breaker verification capabilities is developed. Built on the alternating direction method of multipliers, the novel method maintains compatibility with existing solvers and requires minimum information exchanges across the control centers of neighboring power grids. Numerical tests on an extended IEEE 14-bus model corroborate the effectiveness of the novel approach.