Yes, they are fundamentally the same ecosystem, but the on-premises Cityworks version is being sunset. Trimble Unity Maintain is built on the same core, GIS-centric DNA of Cityworks and fully integrates with Esri ArcGIS. Also, there is a shift in how the software is deployed from on-prem to cloud-based, and what it includes:
Cloud-first SaaS architecture: Unlike older, on-premise Cityworks deployments, Unity Maintain is built as a highly scalable, cloud-managed Software-as-a-Service (SaaS) platform.
Merged tech stacks: Trimble has combined the features of Cityworks, AgileAssets, Pavement Express and Trimble Unity Work Management into this single "Maintain" platform.
Modernized APIs: It features an updated tech stack and API structure designed to make it easier to connect to modern external business applications.
For more information, check out: What happened to Cityworks?