Hello - to answer the question on aliases and PBX routing.

Aliases are a high level conversion that happens almost before any other routing.

So when our switch receives a call to an aliased phone number we convert it to the "true" phone number near instantaneously.

This means ultimately that if you were to forward your primary phone number to say sip:uri@pbx.domain, the alias would follow this same exact path.

So there is no independent separation between SIP URI possible in this implementation with aliases.

If you need independent routing the easiest solution is to set up the desired phone number(s) into a cloud account, in which you can route them to any desired SIP uri (i.e. directly to an extension, or to sip:yourPhoneNumber@your.pbx.domain.com and setup a phone number mapping underneath PBX).

Let me know if this makes sense, thanks!