Not anyone can use it all the time. . .
They are very strict about it first thing in the mornings. They will restrict entry to guests of the three DLR hotels (GCH, PPH, DLH). The only exception to this rule is if you are staying off-site and have eaten breakfast at Storyteller's, you can show your receipt, and be allowed through the DCA private entrance.
Late morning/early afternoon they begin allowing anyone to use the entrance. And anyone can use it to exit the parks at anytime.
Make sure to say hi to Chappy at the entrance if he's there. He's a sweet, sweet CM and a real Disney Treasure.