Issuers selling commercial mortgage-backed securities (CMB securities) use the Treasury market to hedge against interest rate swings. [CMB securities are typically priced at a spread to LIBOR]. Once the CMB deals are priced, the hedges are unwound, which typically pushes prices [of Treasury bonds] higher.

NOTE: Unwinding a hedge simply means closing out a hedge. The way this is typically accomplished is to take the opposite position of the initial hedge. For example, if you buy a bond as a hedge, you would later short that bond to unwind your position. One long + one short of the same bond = 0 position in that security.

Question: When these issuers of CMB securities unwind their hedges, why do prices of Treasury bonds go up?