The state metric MXTTASK is evaluated on a time interval basis. If CICS is in a MXTTASK state at the time checked, the exception will be raised.
Short occurances of CICS max task can go unnoticed by SYSVIEW with regard to reporting it as a "current" condition or state.
The system data collection record (CSYSDATA), will report the number of times max task was reached during an interval. You can also see the MAXTASK by performing the CTASKS command.
As the MXTTASK variable is a SYSTEM-CONDITION schedule, you can see how often (ie: the interval), this schedule will wake up by performing the
CSCHED command from Sysview and checking the EVERY column for how often this is set to check.