The script SYS_INFO can be used to check WP usage over a period of time (1min, 10,min or 60min). For example the below script will message a user if the usage goes above 80%:
:IF SYS_INFO(MQPWP, BUSY, "10") > 80
: SEND_MSG SMITH,AE,"Workload of Automation Engine is above 80%"
This script could be run from a Timed Event at an interval. This will check the percent of usage for the Automation Engine but not individual WPs. Alternatively you can check the status of any WP using SYS_SERVER_ALIVE. This will check if the WP is active. For example:
:IF SYS_SERVER_ALIVE("AE#WP005") = "N"
: SEND_MSG "ADMIN","AE","Work process AE#WP005 is not active!"
Again, you can check in intervals using a Timed Event object.