getEventCallbackNamesByTrigger

import maya.api.OpenMaya as api
from functools import partial

def reportCallbackEventNames(c, *args):
    print c

# install
cbs = api.MEventMessage.getEventNames()
installed_cbs = []
for c in cbs:
    if c not in ['idleHigh', 'idle', 'idleVeryLow']:
        cb = api.MEventMessage.addEventCallback(c, partial(reportCallbackEventNames, c))
        installed_cbs.append(cb)

# uninstall
for c in installed_cbs:
    api.MMessage.removeCallback(c)