Step 2 : BP
a. Bp gets the topic and json array of json records
b. It calls the PubsubBo to get all the subscribers for this topic
c. It loops through json records
d. for each records. loops through the targets 
e. Sends the message to target via the Call activity of the BP

PFA : Screenshot of subscribers to a topic 
Note :  This can be moulded as per the requirement. Each json msg can have a topic instead of the topic being outside of array etc.
You can use your own messages instead of json too if you need.
You can even send messages via the pubsub bo instead of just getting targets. (version attached)
I mean all sorts of adjustments can be made as this is very generic and re-usable

Link to the Code
Download Code

Any issues pls email me nv@nv-enterprises.biz

Example I made aims to make a resusable / generic pub-sub model which is passing a generic json message from start to finish and all bp/bo etc then need to transform / parse as per their own need once they receive the json.  Do let me know if any queries

So this is how the flow works . 
1. Service 
a. Read a csv file, loop through all records
b. In each loop make one json msg and add it to the json array of messages (which is nothing but just an array of text as json is just text)
Property RequestJSONArray As array Of %Text(MAXLEN = 10000);
Property Topic As %String(MAXLEN = 100);


c. End of loop 
Send the array to the BP
This is few lines of code of Service

Class File.BS.FileServiceBS Extends Ens.BusinessService
{

Parameter ADAPTER = "EnsLib.File.InboundAdapter";

Method OnProcessInput(
pInput As %FileCharacterStream,
pOutput As %RegisteredObject) As %Status
{
   set DELIMITER = "^"
   set counter=1 //records read
    set JSONDynamicBPRequest = ##class(Ent.Library.JSON.BP.JSONDynamicBPRequest).%New()
   set JSONDynamicBPRequest.Topic = "TESTCSV"
while 'pInput.AtEnd {
   while counter < 3 {
    set line=pInput.ReadLine()
    if ( counter > 1 ) {
    set req = ##class(%DynamicObject).%New()

     set req.ClaimId  = $piece(line,DELIMITER,1)
     set req.Company  = $piece(line,DELIMITER,2)
set req.ClaimProvider  = $piece(line,DELIMITER,3)
set req.PrimaryInsuranceCarrier  = $piece(line,DELIMITER,4)
set req.EncounterDate  = $piece(line,DELIMITER,5)

$$$TRACE("req.%ToJSON() "_req.%ToJSON())
do JSONDynamicBPRequest.RequestJSONArray.SetAt(req.%ToJSON(), counter)


     k req
    
    }    
    set counter=counter+1
  }  
  do ..SendRequestSync("JSONDynamicBP",JSONDynamicBPRequest)     
  $$$TRACE("JSONDynamicBP loaded : " _ (counter - 1)_" "_$ZDATETIME($ZTIMESTAMP,3,1,6))
  Quit $$$OK
}

}

There is a little modification now what I want to do 

Basicallly I want to read the Event Log (Ens_Util.Log) where type is not in INfo , trace etc

and on every new warning, error etc . send the error msg to my BP - (Which is the pubsub bp)

Is there any service which continously polls for new additions to this log besides the Sql inbound adapter?

Thanx to all and esp to Eduard

I used a mix of Eduard's code, docs, EnsLib.PubSubOperation and some of my code

From my BP -  I am calling the PubSubBo with a response of arrays that gives me targets in a string array 

- BP then sends to all targets from a call inside a loop of targets array. The target of which is set dynamically from context of the loop element.

This gives me an extra functionality of putting some extra logic but most importantly in Visual Trace it doesn't look odd if target is a BP.
If target is a BP and it is forwarded to, from a normal pubsubBo then in visual trace it shows a backward arrrow which is hard to explain to non tech people as it seems its going backward not forward. So forwarding it to targets from a BP is a better and cleaner option .

Can share code to anyone if needed.