According to the policy reference guide on the RIM site:
BlackBerry_Enterprise_Server_Policy_Reference_Guid e.pdf
as you suggested it is possible to restrict access to the onboard GPS via an application control policy, but as that's not how Telmap got there I can't see that it can be that.
I'm guessing, but the next place to look might be in the security policy group of the IT Policy that you have applied (even if it's the default one it's possible that it has been modified). Maybe one of the options in there could prevent access to the GPS? I'd have a look for settings that are not the default - the PDF should show which are the defaults, and if I remember correctly the help on the BES manager does too.