The Gunnery combat skill is used in three cases per the skills section: vehicle/starship weapons, defensive emplacements like turret-mounted weapons, and weapons with targeting computers. However, in the equipment section most explosives and ordnance use the Gunnery skill. I'm not sure how mines fall into one of the three cases in the skills section.
Now consider what careers and specializations list Gunnery as a career skill. The Ace career and all three of its specializations have Gunnery as a career skill because of the vehicle/starship case which makes sense. Other than that, the Squad Leader specialization is the only other career or specialization with Gunnery as a career skill.
This doesn't sound right to me. I would have expected the Soldier Career to offer Gunnery as a career skill or maybe just the Commando specialization. In addition, a character with the Infiltrator specialization might need to go behind enemy lines to perform sabotage which might require the planting of mines.
In general I would expect more characters in AoR to have the option to select Gunnery as a career skill as compared to EotE. AoR characters are more likely to have had formal military training which would lead to a lot more characters trained in Gunnery.