From: Cross Lanes WV USA
AFAIK, counterbattery fire is beyond human control. This is a randomly-generated part of the mech.exe.
Remember this--you command a battalion that is part of a higher (regimental) command structure the player never sees or has direct contact with. This function is abstracted through the support points you get in a campaign scenario, and through reinforcements you can request (though reinforcements cost you VPs).
All things considered, I think the off-board regimental commander is pretty generous, as you have the option (in some cases) to draw upon regimental, divisional or even corps-level artillery, air and naval assets, depending upon your assigned mission. As an example, an amphibious assault can offer 2000 or more support points, but this represents a preliminary aerial and naval gun bombardment lasting over several days. Given this particular mission, I don't think it's excessive.
For other missions, at times it's too much, but you can choose the amount of off-board support you feel is historically appropriate.