Is H1B transfer possible after company withdraws application? (Petition was approved but not "activated")

[JBJS]

Scenario: Got my H1B visa approved from company A after RFE cleared under consular notification, but it is not activated. I no longer work for the company A and cannot get it activated as my employment there has ended. Company A submitted withdrawal and USCIS received it on Nov 28 and is reviewing it.

Question: Can I file a cap-exempt transfer with company B using my company A I-797B approval? Is there a timeline or no. of days within which I need to make this transfer to avoid H1B approval being void/revoked? Are there any risks?

I am currently on F1 and work authorized on CPT till March, 2019 so am not worried about employment or being out of status.

Details: 
Company A petition filed: Apr, 2018. 
RFE received and response submitted: May, 2018 and Aug, 2018. 
I-129 approved with consular notification (I-797B): Nov 6, 2018. 
Company A termination: Nov 15, 2018. 
Company A Withdrawal received by USCIS: Nov 28, 2018. 
Case notification on USCIS case page "Received correspondence and reviewing": Dec 6, 2018.