Given the nature of EHR systems, it's just not realistic to have trial periods, because everything in a hospital is interdependent. Even the relatively small system I worked on did everything from billing, accounting, insurance, HR, inventory management, scheduling, integrations with medical equipment & third parties (e.g. national health systems) with per-speciality workflows and other automation. Most of it isn't even strictly health-related.
Migrating one way is already a multi-year process, making it potentially two-way with low-latency data consistency for the duration of the trial sounds impossible.
In an ideal world, the system would be modular and you could evaluate it piecemeal, but none of the big players are incentivized to make it possible. The standards that do exist are also very lax and legacy systems don't even support those. Something like a goverment intervention is probably required to break this stalemate.
Migrating one way is already a multi-year process, making it potentially two-way with low-latency data consistency for the duration of the trial sounds impossible.
In an ideal world, the system would be modular and you could evaluate it piecemeal, but none of the big players are incentivized to make it possible. The standards that do exist are also very lax and legacy systems don't even support those. Something like a goverment intervention is probably required to break this stalemate.