asterisk users - Mar 2005 - Asterisk & Fritz & Capi & isdn PBX integration : Can I dial out on any MSN I declare ?

Hi,

I'm integrating Asterisk to legacy PBX via ISDN router. If I want to call 
legacy PBX internal extension I need to specify MSN as caller id and local 
number to call.

I wonder if I can cal out via Fritz & CAPI on any msn I want, or are there 
any limitations - I've read something about 5 MSNs limitation and wonder if 
it still holds ?

Thanks in advance,

regards,

Rob.