In FritzBot ET you can use some ET Pro scripting to add extra functionality. In my CAHA_tavern waypoints I needed to focus the non engineer bots to support the top floor when dynamite is planted at Gen A. After implementation I wrote a wiki article (
Making_Bots_Respond_To_Dynamite_Planted_Events) describing how to add a dynamite planted event to waypoints. Now you should verify that the dynamite planted event works with the objective you are talking about and that adding the fake entities to the map script doesn't make the waypoints unstable. Then you can briefly turn off the mentioned plant objective. And I mean briefly since you will also turn off the disarm on that plant objective.
As for the RTCW version of FritzBot sorry all you can do is add enough engineer bots and hope.
One other thing you can do is add an engineer camp action near the place they will have to defuse. But because these have the same priority as other major engr objectives there need to be more engineers on the team than available engineer camps and keep the engineer camp action radii tight like 20-30 units.