I wonder if you may have stumbled upon THE major issue in the mix. I suspect EMT are not at all interested in any reopening. It's simple, really. How long is their current franchise for?
If I were a senior manager at EMT, what are my priorities?...
...Perhaps the only chance of this scheme coming to fruition is when the franchise is up for renewal. Didn't the current operator get brownie points for promising to re-open Corby in the last franchise award (or was that mandated by the DfT in any case)?
I'm not sure if the re-introduction of passenger services was Corby was an initial requirement by the DfT; or if it was an option proposed by the bidders for the franchise - with it then being taken up by the DfT. Either way its been done and has become a success - not only through the reasonable passenger numbers but also by being able to speed up trains from Sheffield/Nottingham through taking up the requirement to call at the stations further south (although those living at said stations miss their direct trains up north!), plus by providing a convenient turn back facility to provide the 5th train per hour on the route.
That said, improvements and changes can happen "mid franchise", such as those delivered through the collaborative efforts of the Lincoln-Nottingham Joint Stakeholder Board, where services between Nottingham and Lincoln were accelerated and stations between Nottingham and Newark Castle were served by an additional service, bringing services between Nottingham and Newark Castle to half hourly frequencies.
A further example is where the terminating London-Derby services were extended up to Sheffield, giving the city 1/2 hourly trains to London.
I would imagine the key difference here is that EMT were already operating the routes and had an interest in improving existing services to meet the aspirations of external stakeholders who were able to then put money where their mouths are.
However Ivanhoe Stage 2 doesn't have an incumbent passenger operator, which is quite progressive with its outlook. It also requires the wholesale upgrade of a freight only line to passenger standards, the building of many stations, a new junction south of Leicester and approximately 2x 156/158s to be sourced/funded.
From my perspective this would sit better with the DfT specifying it as a new project (priced option using their parlance) at franchise bidding time.
However, this improvement will only really make eg Langwith-Sheffield a 'doable' trip, as opposed to 'what a pain, having to wait 45 mins at Worksop, I ain't doing that' trip. For a real look at the passenger potential, we'd need through trains from Mansfield to Sheffield. And, AIUI, that just isn't going to happen with the present local government set up.
If the new services were going to shuttle between Worksop and Sheffield then I would imagine that a codesharing system could operate where EMT operate services to Worksop, where Northern take them over to Sheffield enabling a direct service to run, but the plans indicate it starting back at Retford.
However that could mean that if the political will and funding is forthcoming, that the services could be potentially extended through to Cleethorpes via Brigg in the future.
With regards to advertising the improved connections, then I would hazard a guess that won't be happening - with any growth purely being organic in nature along with word of mouth.