why call administrator now, page-49

That's a bit misleading I think. The $370m is already "in the pool".

The ranking of creditors is (in somewhat simplified format):

Senior Debt
Noteholders
Shareholders

Even if that charge is lifted the ranking of the creditors remains the same.

As I understand it though, the removal of the charge would invalidate the appointment of the receivers and instead the administrator would look after everything.

The receiver only looks after the interests of the senior debt providers and the administrator gets pick through whatever is left. The argument seems to be that if the administrator is in charge - without a receiver - that there may be more money to flow down to the lower ranking creditors (because the administrator has to look after everyone rather than just the secured creditors).

It would seem quite likely to me. Apart from anything it would only be one set of fees rather than two.