We are testing the integration with our partner right now with VG224 & CCM 4.1.x. I saw some document mentioned that the VG224 need to be configured as MGCP gateway, create the fxs port and indicate the SMDI port number. The SMDI port number need to be different for each port e.g. fxs 2/0 port no. 0, fxs 2/1 port no. 1, etc. It depends on how many analog ports for the voicemail. Then create route list/group for the analog ports and create route pattern for (the pilot of the voicemail) and route to the route list. Enable Cisco Messaging Interface and check with your third party voicemail system about the serial port communication parameter such as baud rate, data bits, parity, DN length, etc. Configure them from the Service Parameters of Cisco Messaging Interface. Of course you need to connect the serial between CCM and voicemail system.
We have done the above settings and able to communicate with voicemail system. We got the simulated signal about MWI on from voicemail system but CCM doesn't turn on the MWI. We are still under investigation. You can try those settings and see whether it work.