ECA is not required for endorsement application or for TWP but it doesn't hurt to provide. The endorsement application requirements list is different for each of 4 provinces but none have listed ECA as a required submission.
Further, I wonder why your employer will ask you to submit your passport. The passport will only be required by CIC when they are processing your TWP.
I will share my timeline here:
July 2017 - Job Offer received
September 2017 - Employer Designated
December 2017 - IMM5650 Received(Job was offered to me in July and this is same as job offer but this is what is required to process Endorsement under AIP)
December 2017 - Settlement Plan Received
December 2017 - Endorsement Application sent to Immigration Office
Right now - Waiting on Endorsement for over 1 month.
Getting job offer is the easiest part and once you have the endorsement/approval letter from the province, you have made 90% progress. TWP and PR are simple after you have your endorsement letter from province.
Wow, I didn’t think the province would take that long to endorse the application. Can I ask what province your going to? Mine was sent into PEI this week and as TWP are only taking 3 weeks to process in the UK I was hoping I would be in Canada by end of Feb.