A full alacrity set with pve mods can provide around 1238 alacrity (1088 with pvp mods/implants/ear). This gives you a 13.707% (12.456% with the pvp mods) decrease on your gcd as well as a similar energy regeneration boost. Along with pugnacity and skill tree boosts, this can give you a 25% reduction on your gcd and a similar energy boost. You can also have a special spec that gives you even more speed advantages, if you take the 15% speed boost from the middle tree and the extra 10 energy when pugnacity activates from the right tree. Cap before they get there (which you will), then stealth respec and change gear and you're good to go.
Given that the first cap in Civil War generally decides the match (not always), it gives your team a huge advantage and forces the other team to play aggressive while allowing your team to tank up.