Thank You for Your response. I prepared this as in the example, it is working.
BUT, the problem is, when I want to use angular's service to retrieve data from service (I need this, due to using of $http interceptors mechanism to provide Bearer authentication tickets to web api methods). The problem is, that using this.myService property in the read object definition, causes the runtime error, that this property is not defined. I write the code in TypeScript. Is there any way, to pass the service to the HierarchicalDataSource definition (as asked in another thread: http://www.telerik.com/forums/custom-datasource-transport#nwoZ3-RVSkG5AnLKgnCN7w).