M900 Multicell Deployment - Scenario Advice

Hello

Looking for advice on the following use-case scenario. 

• Separate offices but within walking distance
• Need Snom DECT M65 handsets to work in both locations.
• Continuous RF coverage between both is not required. 
• RF link between two M900 base stations is not possible - seems too far / too many obstacles. 

My question is do we have 2 x M900 operating as separate primary stations? 

In that case, do we need handsets registered on both base stations and is that even possible? 

Thanks