Irvine LOWERS Speed Limits

Given the new PCH bike Sharrows at Aliso I'm wondering, does CALTRANS expect cyclists to pedal the posted speed-limit of 40MPH?  How about 50MPH since that's what traffic is doing?  Meanwhile the city of Irvine have lowered their speed limits in zones where there are bicycles and hot-spots, so why can't CALTRANS do this on PCH?  

Here's a sampling from the city of Irvine:

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• 56 streets will have lower speed limits
• 35 streets stay the same
• 27 streets are newly surveyed and officially posted
• Only 2 street segments will see a speed increase (both on Bosque near the Great Park) 
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  Thank you Council Member Kathleen Treseder for supporting bicycle safety. 

  -LS