The active time has always been an issue. Most of us believe "midnight on 27/11/2014" refers to 60 seconds before 00:01 on 27/11/2014. I think only once has a migration not completed on expected date unless a problem arises
Once the engineering work at the cabinet takes place your ADSL2+ will stop working, as your broadband connection diverts at the cabinet to the fibre link.
I suggest you don't connect your router as soon as the engineer completes their work. It isn't part of their job to ensure you get an internet connection, only that the modem sync's properly with the cabinet DSLAM. But don't wait for Plusnet to notify you as per the email, because they won't do that until they get an Openreach notification of completion. Ring them up, even if it means you have to wait a while, and tell them. Request they activate your account. The reason I say this is that something remains screwed on my account because I tried to connect immediately, and I think it may be because of that.
It is only a minor problem that doesn't affect the running service, but doesn't seem to be soluble. (The 15-minute wait described in the instructions that come with your Plusnet router never ended and I had to ring them for help).
I also strongly recommend you phone Eclipse as well to make sure they know the migration is complete. It can help prevent account problems with them in the future.
My broadband basic info/help site - www.robertos.me.uk
| Domains,site and mail hosting - Tsohost
Connection - Plusnet
UnLim Fibre (FTTC). Sync ~ 56.4/14.5Mbps @ 600m. - IPv4BQM
"Angels can fly because they can take themselves lightly."
- G K Chesterton.