I just found this out accidentally earlier! See video at the bottom of this thread: This is not obvious (to me at least) as I just stumbled into the solution earlier today (and I was using it during beta). I went as far as finding a clipboard metadata viewer to report a bug with details on the different data types Windows can paste as... then accidentally got it working.
You might well be missing something! I was. Could not get pasting from LibreOffice Calc (Windows 10, 64bit) to work - it would just stick everything in the first Publisher table cell. Tried every option under Edit > Paste Special. Maybe you're just pasting it wrong. Ensure you are not currently editing text in the cell, that you don't have any TEXT in the cell selected, but the CELL ITSELF must be selected, and then hit paste. See attached video. publisher-pasting-into-table.webm