Hershel,
You have to keep in mind that non-supported SIP phones are handled the same as analog phones in the Mitel 5000, but even then not all feature codes are usable with SIP devices. As I have never seen an Aastra SIP phone I don't know what its capabilities are or how you would program the feature codes into it, but for the most part, in theory, you would need some sort of hookflash followed by the feature code for some features and just the DTMF for others, just think "how would I do it with an analog phone" and then try it. If you can't get it to work manually then programming it as a button will most likely not work either. The problem comes in how SIP sends its signaling and commands back to the 5000 which reduces the amount of compatibility, as far as feature functionality, it will have with any system is wasn't designed for.
Unfortunately I know that probably wasn't very helpful, but it is the best answer I have when it comes to these sorts of scenarios.
Sorry,
TE
