arca starts at 4 am. IB would allow you to trade since then, but spreads can be kinda wide :D
http://www.nyse.com/productservices/nysearcaequities/1157018931781.html
Pre-Opening Session: 3:30 a.m. ET
Limit orders can be entered and will be queued until the Limit Order Auction at 4 a.m...