To answer a couple of questions as best I can (I am currently waiting to hear from the officers board in this occ.)...
Signals Officer (84) is the land designation and CELE (Air) (83) is the Air Force designation.
What are the differences? Well, as I am not there yet I can‘t tell you for sure.. but the website gives some good examples.
83: As a CELE (AIR) officer, you will become involved with numerous high tech electronic systems that support our Departmental command and control environment such as the computer networks and communications systems that support surveillance/ reconnaissance/intelligence, data/information/knowledge management, air traffic control, the full spectrum of terrestrial radio and satellite communications from HF to EHF, radar and navigation, electronic warfare, cryptography, electronic intelligence, and communications and network security
84: As a Signal officer, you will become involved with Army Command Support systems such as Land Force Command, Control and Information Systems (LFC2IS), Intelligence Surveillance Targeting and reconnaissance (ISTAR) systems, the full spectrum of radio systems from HF to EHF, electronic warfare systems, cryptographic systems, and systems for communications security.
So there is a fair bit of difference.
As for where you will be posted, well I can only partly answer that for the army, as that is where all my questions have been directed. As far as I know, the places you mentioned (Shilo, Edmonton and Gagetown) are fairly popular, as well as Petawawa, Kingston, etc... however, it is possible that you oculd be attached anywhere, to any unit (again, afaik).
It is possible to get posted overseas. When I had my interview, the capt. said that Signal men were among the first in bosnia, setting up some of the critical infra-structure (anybody, please correct me if I am wrong).
I know I didn‘t touch most of your questions, but I hope I answered them somewhat...