You should not use ContentControl try using ContentPresent
<Grid x:Name="MyGrid">
<ContentPresenter x:Name="ContentControl" Content="{Binding}" Style="{StaticResource MyContentControlStyle}" />
</Grid>
And behind the code you have to explicitly have to say apply template in order to get it
ContentControl.ApplyTemplate();
var dataGrid = ContentControl.ContentTemplate.FindName("dataGridFromDataTemplate", ContentControl) as DataGrid;