Hi Hensell,
Small questions can sometimes be most interesting to think about.
I have been told in the past, and you are correct in your comment, that a cluster must be no more than ten AP 500's within the same cluster.
But a Layer 2 LAN broadcast domain, spread over multiple managed switches, can house many clusters.
For the cluster members to communicate, APs must be able to communicate over the same management VLAN.
They will exchange configuration information and other information.
Having said all this, I would doubt if you wanted to manage all twenty-five AP via the default data VLAN.
If it were my UC560, I would create another vlan on the UC560 for the purposes of allowing the 25 AP's to create appropriate clusters and get an IP address. It maybe that cluster members will reside on different POE switches.
There is a wifi deployment guide for UC500, but for a good reason doesn't mention the numbers of AP's you can have on the network. It is worthwhile discussing engineering the solution of this with your trusted Cisco Partner.
http://www.cisco.com/en/US/docs/voice_ip_comm/sbcs/deployment_guides/voice_over_wireless/sbcs_20_vowifi_deployment_guide.pdf
Personally, if engineered correctly, i can see no real issue with multiple clusters in a hospital environment.
Dave Hornstein
Cisco Systems Engineer
Research Triangle Park
Raleigh NC
