Hello,
While "Talking is a Free Action" has become something of a role-playing game trope, A Time of War does define the nature of communication across Incidental, Simple, and Complex Actions.
Per p. 166, a character may perform up to 5 Incidental Actions per turn. Incidental speech is also defined on the table on p. 167 as one word. Thus, a character may only say five words per turn as Incidental Actions. Not exactly a lot of communication, but just enough to say a quick like "Bob! Look out behind you!" More than that, and the character is entering into Simple or even Complex Actions.
Hopefully, this helps.
Thank you,
- Herbert Beas
BattleTech
Catalyst Game Labs