The BAR Team unit in St Mere Eglise has the Opportunity Fire symbol, which is a red cross hairs enclosed in two blue semi-circle arcs with arrows. This symbol is very clearly displayed in the base game rules.
The term "overwatch" is not used anywhere in the rules to my knowledge, though I have seen threads using that term instead of opp fire (which is confusing BTW).
Page 17 of the English 1.2b rules clearly has his as the opportunity fire symbol
It may function like overwatch in other games but it is clearly Opportunity fire as pisqueeter points out.