[Sheepdude]

True - that cvar didn't exist until a recent patch.

So to summarize:

Warmup Start: Second occurrence of "round_start" event. (occurrence by "mp_do_warmup_period" and "mp_do_warmup_offine" [sic])
Warmup End: Third occurrence of "round_start" event (length determined by "mp_warmuptime" (min 5.0))
Halftime: "announce_phase_end" event (length determined by "mp_halftime_duration")
Demo halftime: "announce_phase_end" event (length determined by "mp_ggtr_halftime_delay")
Match end: "cs_intermission" event and "cs_win_panel_match" event (length determined by "mp_match_restart_delay")

Start warmup command: mp_warmup_start
End warmup command: mp_warmup_end

Please, correct me if I'm mistaken.