If it works, then it works. It won't hurt to try.
I get maybe 3/4 mile with my GMRS Motorola radios. That's enough to cover from camp out to any of our blinds. This used to be a MUST, because cell coverage was so poor. Nowadays, it's more about nostalgia for us.
I was big into CB back in the heyday. I was reaching out 25 miles at times on my mobile-- normally about 2-5 miles. However, a hand-held walkie talkie is probably not going to cut it.
If these are static locations you're talking about, you can rig a unit with an elevated antenna and blast away. Your only worry will be keeping it powered, but a deep discharge battery and a solar panel will be fine. Will you be able to talk to the base? It's all about height, distance and conditions and tuning the rig properly.
