Does "show logging" report "logging to [syslog-server-ip-addr]" on the 4500s?
Assuming you have root access on Solaris, does "snoop -v -s 514 -t a -d [interface-ciscoworks-listens-on] [one-of-the-4500-mgmt-ip-addrs]" show any traffic?
Since you're referring to dmgtd.log, I assume your syslog server is actually the CiscoWorks LMS server. In that case, are the 4500s still managed as "Normal Devices" in RME? Do they have the new/correct IP addrs in DCR? IME, RME doesn't report syslogs for devices it doesn't manage.
A relevant log to look at is SyslogCollector.log, particularly after enabling debug in /opt/CSCOpx/MDC/tomcat/webapps/rme/WEB-INF/classes/com/cisco/nm/rmeng/csc/data/Collector.properties (and then restaring SyslogCollector).
BTW, I don't think LMS 2.6 is supported on Sol 10. Only LMS 3.0 is.