Setting VCS Checkout rules using parameter from dependency build

I have 2 build configurations with a snapshot dependency.

The first build has a build step which outputs a service message to set a parameter value.

When the build is finished I can see the parameter value was updated correctly.

In the dependent build I set the VCS Checkout rule to use the same parameter using %dep.BuildId.ParameterName%

I tried setting the parameter as Config, System and Env, and in all cases the parameter value was not used in the checkout rule.

The parameter value is the actual checkout rule I want applied, i.e.

+:Folder1

+:Folder2

Instead of checking out just the specific folders the entire VCS Root is checked out.

Update:

I created a system parameter in the containing project and this parameter is updated correctly during the build and the value is being used in the dependent build.

I also managed to update the checkout rules of the dependent build using REST API, thereby the parameter is not even necessary anymore.

However, for both the parameter and the REST API method, I can't get Teamcity to accept newlines, since the checkout rules are newline delimited.

I tried using |n (pipe), but it is only translated to a newline when updating the parameter during the build.

When I try to use this parameter to update the checkout rules the newlines are lost.

Update 2 (For anyone coming here searching for an answer):

After some more tinkering and web searching I got it to work by updating the checkout rules using the REST API with curl and sending the data as xml with 
 as newlines.