What is required to change bail at the conclusion of a preliminary inquiry

The judge hearing a preliminary inquiry can, at the conclusion of the inquiry vacate any existing bail order and make a new one: Criminal Code s. 523(2). 

R. v. Prete, [1987] O. J. 2480 is usually taken to say such an order will be made only if there material change in circumstance from the existing order. 

Other cases seem to consider the preliminary inquiry judge to be holding a hearing de novo. So R. v. Grier, 2010 ONSC 6934 holds:

[4]               The applicant suggests that errors were committed both at first instance and at the de novo hearing.  In my view, the de novo procedure provided for in s.523(2)(b) of the Criminal Code has the effect of vacating the original detention order made by the learned Justice of the Peace.  It is an entirely new hearing that incorporates the testimony called at the preliminary hearing which, in turn, has been open to the opportunity for cross-examination.  As well, it is subject to review to this court: see s.520(1) of the Criminal Code.  In the result, the only matter properly before me is the review of the detention order made on June 4, 2010 as the order dated December 14, 2009 has lapsed.