As already clarified by direct contact:

The push cells are not meant to be modified directly by application code; they may only be removed and replaced by newly created cells.

However, the simplest way to have the same cells refer to different items is to reassociate the cells with different tables subsequently and tag the cells with an index.
For instance, with the item="1" attribute, the cell always refers to the first subscribed item of the currently associated table.
This is shown by the included StockListDemo page, where clicking on the "next 15" link reuses the same cells for different stocks.

Note that when indexes are used for the "item" attribute, the item names must be specified in the table constructor, i.e. the form
new OverwriteTable(null,null,"MERGE");
cannot be used, but something like
new OverwriteTable(["my_item1","my_item2"],null,"MERGE");
should be used instead.