Lights growing brighter and dimmer

You'll need to name the lights that will grow brighter or dimmer. Name them all the same thing. For example, blu_lt1, or red_lt1. Then when a team takes the point, add outputs from the trigger_capture_area OnCapTeam1 that turn the lights on and/or SetPattern (patterns step up in brightness from a which is dark to z which is bright).

For example:
trigger_capture_area -> OnCapTeam1 -> blu1_lt* -> TurnOn
trigger_capture_area -> OnCapTeam1 -> blu1_lt* -> SetPattern -> bdjhmnoxrs-> 0 sec
trigger_capture_area -> OnCapTeam1 -> blu1_lt* -> SetPattern -> srsrsr -> 2 sec
trigger_capture_area -> OnCapTeam1 -> red1_lt* -> TurnOff

Should be simple, but you'll have to play with the actual patterns and timing to get the "flickering up with power" effect. Basically you'll want a flickering, brightening pattern, then replace that one with a steadier pattern after a second or two. [Edit] And optionally, you might want a flickering, dimming pattern for when the lights go out/dim.

One warning: naming a light makes it dynamic, which is a lot more resource intensive. So you should NOT do this to every single light but only a few in key areas to create the effect.

Kep

If you don't want to have an excessively large lightmap file (the Earkham's method would work quite efficiently) don't forget that entities such as env_sprite and point_spotlight are a lot cheaper, and are more obvious. Use earkham's method, but do that as well.

Personally I'd just create some sparks in the lights, and have a second set of lights which turn on.