Rob Horne has previously answered a similar question at the following link;
Essentially the suggestion is that the ‘time bar’ period commences when the applicable legislation comes into force (as stated on the legislation). Prior to this date the ‘proposal’ may be subject to consultation or debate, whereby the content could be subject to change prior to becoming legislation.
With regard to the PM’s failure to respond to the notification, the further notification means that the matter is treated as though it were accepted by the PM, provided the ‘further period of time’ passes without a response (clause 61.4), so the notified matter would be a CE. The PM could notify a CE under 60.1 (8) as a ‘changed decision’ although I’m not sure if this could apply, as the previous ‘decision’ was not to respond to your notification, which may not be considered as a ‘decisive action’ under the contract.
Remember that if you have main option C, D or E, the Disallowed Cost provisions refer to cost incurred only because an early warning was not given, so be aware of this if different measures could have been taken to address the new legislation and an early warning was not given.