Actually I used some TCs for SIP trunk configuration and system documentation for R10.3.
Check OXO10.3_sd_VoIPServices_8AL91205USAC_1_en.pdf file and §5.2.4 (mainly 5.2.4.10-5.2.4.11)
For incoming calls in Pubic Numbering plan you assign public numbers to internal numbers and choose according SIP acc index. That's all.
If there is a problem with CLIP for outgoing calls I use easiest way - Alternative CLIP for an extension.