ok on Linux the ( is a special character and needs to be escaped try the following which worked for me (well I had no agents to mount but the syntax was accepted)
java -Duser=admin -Dhost=127.0.0.1 -Dport=5001 -jar CLWorkstation.jar mount agents matching \(.*Websphere.*\)
Executing MountAgent Command.....looking for agents matching (.*Websphere.*)
Have this pack added to our 10.5.1 environment and try running a similar command java -jar CLWorkstation.jar mount agents matching (.*Websphere.*) but I get -bash: syntax error near unexpected token `(' as return.