I think so; when I used them I went into build mode, then collections and placed the objects on the lot, saved and exited the lot, then re-entered and everything was fine.
Here are the instructions from the website - just to be sure you get the ones that are right for you!:
* Unzip into \Collections folder *
Not \Downloads, like you normally do!
Base game and/or early expansions:To use this in Pets or Seasons you must go into BUILD MODE first and THEN Collections. NOT for use in Bon Voyage or FreeTime, see below.
Bon Voyage & FreeTime:If you download a lot with no mailbox/trashcan when you try to move a sim to the lot, it will not go into live mode. Just place the items and exit to neighborhood, re-enter and then proceed as normal.
Apartment LifeFor Apartment Life Mailbox to work properly you must delete the following files if you have them:
In the COLLECTIONS folder 0x6e870b24.package
In the Downloads folder SEDD_BuyMailboxBV.package
Note that all building rules still apply for this buyable mailbox. If you're not using the boolProp aptsublotspecifictoolsdisabled false cheat code you'll have to be in residential zoning placing the mailbox.
If you're in apartmentbase zoning when you pick up the mailbox from buy mode it will already be the apartment style, but you'll still have to use the move_objects on cheat code to place it on the tree lawn. There is no redux of the trashcan at this time as the BV one seems to be okay. If you've removed all your CC except the trashcan and you experience a problem with it, let me know.