If your want to manage the settings inside de Microsoft Online Sign-In Client (used with BPOS) through Group Policies, you can download a Active Directory Group Policy Object here.

As stated on the Microsoft Online Services Team Blog:
This file is provided as-is and is not supported.  It has been tested and works properly, however it has not gone through official Engineering sign-off.  Once signed off it will be published to the Microsoft Downloads site, so stay tuned for an official version.

Settings you can manage:

• Enable Sign In to remember the username of the last signed in user
  This policy should be Enabled when your user’s Online Account Name should be displayed each time the Sign-In Client is launched.
• Enable Sign In to remember the password of the last signed in user
  This policy should be Enabled if your Online user’s password should be remembered and populated each time the Sign-In Client is launched.
• Enable Sign In to automatically sign in the user
  This policy should be Enabled if you want the Sign-In Client to automatically sign-in once Windows is started.
• Enable Sign In to automatically start when the user starts Windows
  This policy should be Enabled if you want the Sign-In Client to automatically launch after Windows starts.
• Enable Sign In to automatically minimize when the user signs in to Sign In
  This policy should be Enabled if you want the Sign-In Client to automatically minimize to the Windows.
• Enable Sign In to show alerts when a new update is available for Sign In
  This policy should be Enabled. It provides visible popup notifications when a Sign-In Client Application update is available.
• Enable Sign In to show alerts when a new configuration is available
  This policy should be Enabled. It provides visible popup notifications when a Sign-In Client Application Configuration update is available.

http://blogs.technet.com/msonline/archive/2009/02/09/microsoft-online-sign-in-client-adm-group-policy-object.aspx

/* 26.05.2010: I just got noticed in the comments that the link isn’t working anymore, thx Darren*/

Some things it can manage:

• Enables Sign In to remember the username of the last signed in user. This policy should be Enabled when your user’s Online Account Name should be displayed each time the Sign-In Client is launched.
• Enables Sign In to remember the password of the last signed in user. This policy should be Enabled if your Online user’s password should be remembered and populated each time the Sign-In Client is launched.
• Enables Sign In to automatically sign in the user. This policy should be Enabled if you want the Sign-In Client to automatically sign-in once Windows is started.
• Enables Sign In to automatically start when the user starts Windows. This policy should be Enabled if you want the Sign-In Client to automatically launch after Windows starts.
• Enables Sign In to automatically minimize when the user signs in to Sign In. This policy should be Enabled if you want the Sign-In Client to automatically minimize to the Windows SysTray.
• Enables Sign In to show alerts when a new update is available for Sign In. This policy should be Enabled. It provides visible popup notifications when a Sign-In Client Application update is available.
• Enables Sign In to show alerts when a new configuration is available. This policy should be Enabled. It provides visible popup notifications when a Sign-In Client Application Configuration update is available.