How to retrieve sprite data from BANK4?

Here’s a snippet of eleven source code from the xanadu demo that accomplishes this:

  #declare SPRPTRBNK = $d06e
  #declare SPRPTRADR = $d06c

...

  ' enforce sprites into BANK4 and SPRPTR16 bit turned on
  poke SPRPTRBNK, 4+128
  wpoke SPRPTRADR, 0

NOTE: That +128 is the turning on of bit7 (SPRPTR16).

(the full source can be perused here)