yeah very likely it is late because of the holidays....
and if an agency is helping handle the case, it should be fine..
but what I want to say is, it is possible that the letters go lost.. Here is an example: I did not get the Acknowledgement Letter (FN letter).
I emailed them and they wrote back telling me my file number (and that they were not going to send me that letter again). :-(
So, wait a bit longer maybe. when you decide that you cannot wait any longer, email and ask them what's happening!!