According to an OG forum report (minor spoilers) the trailer has several scenes between Jack and Gwen, with Jack saying, "Torchwood is separate from the government, outside the police, beyond the United Nations." There is also a police official who makes reference to Jack failing to report for duty and dissapearing on January 21st, 1941. There are some shots set underground at the Hub, and one dramatic one featuring the Captain standing on top of a tower. The music and tone throughout have an X-files feel to them.
A trailer is worth a million words, so let's hope this is released soon so I won't have to type them.