Background: Dementia biomarkers are increasingly being introduced to improve diagnostic accuracy, yet their integration into routine clinical practice remains complex, particularly across diverse health service contexts. The Enhanced Dementia Diagnosis (EDD) study investigates the real-world implementation of blood biomarkers, volumetric MRI reports, and digital cognitive assessments across rural, regional, and metropolitan clinics. Aim: To examine the implementation of the EDD study across rural, regional, and metropolitan case clinics, and to explore the experiences of clinicians, clinic staff, and the implementation team. Methods: A qualitative multiple case study was conducted using semi structured interviews and observations across three clinics and the implementation team. Approximately 10 interviews were conducted per site and with implementation team members, with some participants interviewed longitudinally to capture implementation over time. Data were analysed using thematic analysis mapped to the Systems Engineering Initiative for Patient Safety (SEIPS) framework. Results and conclusion: Findings demonstrated variation in the EDD work system across sites. Differences were evident across organisational structures, clinical environments, and in task workflows such as referral processes, screening, and case conferences. Service geography influenced implementation, with greater patient travel required in regional and rural contexts. Key barriers to implementation spanned SEIPS components, particularly relating to workflow coordination and local context. Enablers included iterative process adaptations, with sites implementing practical changes tailored to their clinical processes. These findings highlight how context-specific work system factors shape implementation and equitable access to novel dementia diagnostics. They underscore the need for flexible, locally responsive implementation strategies when scaling diagnostic innovations across diverse health service settings.