Well, there is a memorandum that is published (I don't know about the Memo that your lawyer says because does not appear in several websites neither at USCIS) and says that nobody will be granted a green card until the background/name check and all security checks are done and that does not depend on USCIS.
The timeline depends on your District Office. There are some- like some offices at California- that their processing time is very fast and people even get their interview notice before the get their EAD. Not all are like that.
If your lawyer is so kind would be good that he send to you the Memo so you can share it over here, and be sure what is about.