As urban underground utility networks shift from incremental expansion to the renewal of existing assets, their governance faces a core question: Whether independently established discipline-specific conditions can become jointly feasible and remain effective once they enter shared underground space and a continuous engineering chain. The corresponding engineering-science logic is to successively transform dispersed discipline-specific conditions into jointly feasible conditions, executable project conditions, and conditions for subsequent engineering decisions. This study defines a cross-utility engineering linkage as a situation in which a discipline-specific condition materially alters the feasibility of another facility. Along the three stages of joint judgment, project execution, and subsequent updating, four condition states are identified: independently feasible discipline-specific conditions, jointly feasible conditions, executable project conditions, and conditions for subsequent engineering decisions. Three condition transitions connect these states across the engineering chain, while common-boundary identification, implementation-path differentiation, governance translation, and cross-period feedback explain the corresponding transition mechanisms. The results indicate that discipline-specific compliance cannot substitute for joint checking at common boundaries; implementation paths are determined, under non-negotiable safety baselines and relevant discipline-specific constraints, by the degree of spatial lock-in, data reliability, and construction windows; conclusions from joint checking become executable at the project level only after they are incorporated into project documents, assigned to responsible entities, and used to modify project conditions; and cross-period feedback is established when as-built and operational information is retrieved and used in subsequent projects to revise engineering decisions. For engineering applications, the framework can therefore be used to identify common boundaries, select implementation paths, incorporate joint-check conclusions into project documents and assign responsibilities, and use as-built and operational information to update subsequent decisions. Accordingly, disciplinary conflicts, discontinuities in project implementation, and failures in information reuse can be interpreted uniformly as interruptions in the transformation of engineering conditions. Systemic governance can thus be evaluated at a directly testable engineering scale: Whether engineering conditions remain effective across successive stages. This engineering-science logic can provide a basis for the transition of urban underground utility networks from facility-specific management toward lifecycle governance at the infrastructure-network level and, after sustained validation, may further enrich basic understanding of the development and long-term operation and maintenance of modern infrastructure networks.