Edit: Perhaps the radios are completely controlled by the script file? If I run a map with the sdk_frontline script without doing anything more than adding spawns, and a flat brush, it creates radios at a default x/y. Regardless, I feel like there is supposed to be some kind of visual representation of them in Hammer, and the errors I get below in the Spoiler seem out of place as not everyone has them as I found out.
Alright, this is a technical question on the mapping end and has to do with the radio as the last objective to "capture." Whenever I've attempted to open a map with the radio included, Hammer appears to consider it an invalid brush and completely removes it, making it impossible for me to figure out how it works and how I can implement in a map.
[Blocked Image: http://puu.sh/rAg5v/f7bffb4d6a.png]
You can see below when I make my way to table, it's not there and I can't edit anything associated with the radio (it somehow still appears in game when compiled though....)
[Blocked Image: http://puu.sh/rAfuq/24bb525ba9.jpg]
Testing for consistency with the issue, I decompiled dog_red and ran into the same issue with a bit more:
[Blocked Image: http://puu.sh/rAgek/7e4343d453.jpg]
(Some context on location, this is inside the farthest back bunker with the small table the end Radio objective should be spawning on)
The spawn point mdl fails to properly render. Although this hasn't happened with smaller maps like the example ones given to demonstrate the different gamemodes.
Forgive me for the screenshot method but I don't know how to get the text copied from the Hammer messages window 
:
Spoiler [Blocked Image: http://puu.sh/rAgQP/a38c5641c0.png] [Blocked Image: http://puu.sh/rAgVL/367cd4f025.png] [Blocked Image: http://puu.sh/rAgY8/4af639cf44.png]