The dual carriageway bypass of the exiting A46 (Fosse Way) was officially opened a couple weeks ago and the main line has existed here on OSM for some time - now the junctions from Flintham to Owthorpe are completely mapped (looks like Roehoe, Widmerepool, the junctions to Fardon are too - don't think there are any more) alongside all the open bridleways, tracks, and local roads alongside the A46 from just north of Roehoe to Farndon.
All we need now is for Sustrans to sign NCN Route 48 (fittingly called "Fosse 2") which is supposed to be routed from it's current terminus at Nether Broughton to the Grantham Canal then along the old Fosseway to Newark on Trent. The bridleways (actually really wide gravel tracks in the main - nearly as wide as the former A46 itself!) and access tracks make it pretty obvious where the route will be going from Flintham to the Grantham canal.
From Farndon to Flintham looks like it will be the old A46 Fosse Road itself.
From Flintham to Red Lodge it looks like it will be the bridleway on the western side of the new A46, then over the Red Lodge junction itself to join a very short section of the old A46 past the Lodge, then on half (the carriageway still has the old centre lines and cats eyes at one of the edges of the new road way!) the former A46 all the way down to Margidunum (with a short gravelly section round the new bridleway bridge between Car Colston and East Bridgford).
From Margidunum (Southbound exit) to the former Margidunum junction (still in use as the main link between the A46 southbound and A6097) it looks like a cycleway is currently under construction (obvious at both ends, less so in the middle).
From the old Margidunum junction to Bingham it's a bit less obvious - on the eastern side it looks like a cycleway might be under construction (right next to the west of the old A46) but it's a bit hard to tell (however there are some new cycle tracks round the roundabout itself which link in with this) - however for the time being you can use the new bridleway to the west of the new A46 - from Margidunum to the entrance for (RAF) Newton it's a tarmaced road subject to an unusual 25 mph limit, then you are put onto a nice new bridleway to the new Saxondale Bridleway bridge and NCN15.
The mess between Saxondale and Bingham junctions on the A52 (The village of Bingham being adjacent to the junction named Saxondale; and the village named Saxondale being adjacent to the junction named Bingham!) will hopefully make itself clear soon (I believe a pedestrian crossing is supposed to be going in there), and from there you join the former A46 which is now used for local roads until you reach a slip road (currently blocked by a locked gate at the top - just carry on south a tad and enter the old picnic area through the old car park) just north of the Grantham canal crossing from where you can access the canal and the rest of Fosse 2 to Exeter if you wish.
Alas if you carry on down the old A46 the parallel tracks take a break between Stragglethorpe and the Colston Road overbridge, but from there southwards you have a bridleway (which starts as an access road - three lanes in places, the former A46 being left un-changed until it's downgraded to a bridleway at Owthorpe, a little futher south you then have a detor via a farm track and Lamming Gap lane before once again getting to the A46 and a bridleway to Roehoe which is still under construction).
All in all not a bad job for a scheme which, back in 2008, wasn't due to start until 2015 but was then brought forward as an economic stimulus. Should be fully finished by late summer giving the workers a break before work starts on the A453 which will also be downgraded to allow for the extension of NCN Route 15 once it had finally been dulled!
Only grumble with it from a cycling point of view is that the gravel is VERY loose, a fair bit of sliding about - hopefully it will get compacted down with use!