It’s possible with Asterisk, but defeats the purpose of the access control system. You should discuss with the building manager acceptable means of authenticating your guests. As the entry panel won’t have DTMF, I think you will need to use speech to text to enter an access code. You should change the code between guests.
I suppose you could get the guests to ring the Asterisk system, authenticate themselves using a DTMF code, and then give them, say, 30 seconds, in which a call from the entry panel will be accepted.
Does the building not have some sort of provision for couriers, etc. to gain access, e.g. with a key pad and a one time code?
What you are proposing may invalidate the building fire safety approval, or insurance, which is why it is essential that the building mangager approves it.