I have not used the 3905, only the 796X and 794Xseries, and that was several years ago. I haven't touched them since. Since the 79XX sets were supported at the time, I took the "standard" provisioning file created by 3CX, then modified it to add additional line keys, and then created a dialplan based on examples i found on other sites (including Cisco's), and my own needs. I cam across a number of template examples on sites advising on how to use the sets on "other" SIP based PBXs.
It is best not to post any provisioning files on-line if they contain passwords or other information that can be used to compromise your system
I'm assuming that the set has a SIP load that will work with 3Cx (or Asterisk), and not just a Cisco Call Manager system.