Asterisk share isdn pri

I have multiple offices with ISDN PRI’s that are only partially used (they were installed for Video Conferenceing and at most only use 10 Channels, normally only 3 or 4). Is there a way to have Asterisk share these ISDN PRI’s? I have done a little searching and found some documentation that says multiple TE1’s can connect to one ISDN PRI, but the documentation for the Digium ISDN PRI Cards doesn’t mention if they have have internal NT1’s or need an external NT1 and act as a TE1?

Tim B