I would suggest to create 4 contact groups. Then put the hosts into these 4 contact groups and also assign these contact groups to the users.
I.e. put hostA1, hostB1, hostC1 into contact group “Svr” and assign all users in group userSvr that contact group. By default every user can see only “things” (hosts and/or services) for which he/she is a contact. (Except admins, they can always see everything, no matter their c.g.)
See also the docs: