i just stumbled across this topic on accident. Coincidentially I had to solve a similar problem last year.

DISCLAIMER:

1. english is not my native language, so if you find any typos you are free to keep them :-)
2. This approach feels like an ugly hack. In fact it is. So use it at your own risk. For me though this approach has proven to be stable for over a year now.
3. I am fully aware of the fact that i am necroing an old thread. Maybe someone will find the information useful anyway.

Scenario:

• SSIS packages from multiple solutions are deployed to the SQL Server and reside in the "Integration Services Catalogs"
• There is a need to call specific packages residing in solution "b" from packages that reside in solution "a"
• There is a need to pass data between those packages.
• The selection dialog for the SSIS package execution task does not allow us to select packages from an "external" solution

My approach was as follows:

1. for each variable you need to pass cross-solutions: create a package parameter in the receiving (=called) package
2. from within the parent (=calling) package do the following steps

a) using EXEC SQL Task: create a new SSIS execution directly in SSISDB. We do this to circumvent those nasty restrictions the "Execute SSIS" task within SSIS tries to impose on us.

EXEC [SSISDB].[catalog].[create_execution]
  @package_name= @SSISPackageName --SSIS package name TABLE:(SELECT * FROM [SSISDB].internal.packages)
, @folder_name=@SSISFolderName --Folder were the package lives TABLE:(SELECT * FROM [SSISDB].internal.folders)
, @project_name=@SSISProjectName --Project name were SSIS package lives TABLE:(SELECT * FROM [SSISDB].internal.projects)
, @use32bitruntime=FALSE
, @reference_id=NULL --Environment reference, if null then no environment configuration is applied.
, @execution_id=@ChildSSISExecutionId OUTPUT --The paramter is outputed and contains the execution_id of your SSIS execution context.

b) Set required parameters for the child package. This is where we send over our data from parent -> child package parameters.

In this exaple we populate two parameters (object_type 30) called "ParentPackageExecutionID" and "ServerName", as well as one Environment setting (object_type 50).

Also note that we need to provide the execution_id (stored in @ChildSSISExecutionId in this example) that was generated in step a) to ensure that our settings are attached to the correct SSIS run.

EXEC [SSISDB].[catalog].[set_execution_parameter_value]
  @ChildSSISExecutionId  -- The execution_id value we received by calling [create_execution]
, @object_type=30  --30 is Package Parameters, you can also use 20 for Project parameters or 50 for Environment
, @parameter_name=N'ParentPackageExecutionID'  --Parameter name
, @parameter_value=@ParentSSISExecutionId

-- set SYNCHRONIZED Flag to wait for Child process end
EXEC [SSISDB].[catalog].[set_execution_parameter_value]
  @ChildSSISExecutionId
, @object_type=50
, @parameter_name=N'SYNCHRONIZED'
, @parameter_value=1

-- set SSDB Server Name
EXEC [SSISDB].[catalog].[set_execution_parameter_value]
  @ChildSSISExecutionId
, @object_type=30
, @parameter_name=N'ServerName'
, @parameter_value=@ServerName

c) After finishing our configuration we need to tell SSIS to actually run our package. Once again we need to supply the execution_id here.

EXEC [SSISDB].[catalog].[start_execution]  @ChildSSISExecutionId

d) optional (but advisable): monitor the execution of our child package and throw an error if needed. This allows the parent process to react in case the child process ran into an issue.

DECLARE @ErrorMessage NVARCHAR(MAX)

SELECT @ChildSSISExecutionStatus = [STATUS]
  FROM [SSISDB].[catalog].[executions] WHERE execution_id = @ChildSSISExecutionId

IF (ISNULL(@ChildSSISExecutionStatus,0) <> 7) 
BEGIN
  SELECT TOP 1 @ErrorMessage = 'Execution path ' + execution_path + ' failed with error: ' + [message] 
    FROM SSISDB.catalog.event_messages 
   WHERE operation_id = @ChildSSISExecutionId 
     AND event_name   = 'OnError';
  THROW 50000, @ErrorMessage, 1
END

Hope this helps.

Kind regards, Chris