Yes, it is easy to do with TES4Edit! I sure do hope it
was land records you were asking about

You need to:
"Copy as override" the land records from the
Hammerfell worldspace into a new ESP
Note down the Form ID of each
Tamriel worldspace land record you want to replace (quickest way to do this is to open a second TES4Edit session and just load Oblivion.esm so you can look up the vanilla Form IDs in one session while editing in the other)
"Change Form ID" on each land record to that of the corresponding Tamriel worldspace land record
Change the Cell entry for the land record to match that from Oblivion.esm (after changing the Form ID, click on any other record in TES4Edit then click back on the land record, this will display the vanilla record alongside your record - now you can just drag the entry from Oblivion.esm's Cell field into the new ESP Cell field)
Repeat for all the land records
Save and exit TES4Edit
Done.