From a post by an English lad living in des Ecrins on Sun Apr 2nd here:
That is the same single-lane diversion that we used last year to go between Briancon and Grenoble - no guarantee that it's open for use. Also worth noting that it's a 3.5 ton limit, so theoretically the minibus cannot officially use it (and would be a cause for being fined if caught, remote as that may be).Road news: the Tunnel from Grenoble to Briancon via la Grave is still under repair, meant to be finished 16th July?? There is the temporary road but even when it is open the signs say shut (its more for local to get to work) a bugger if you have driven up from grenoble to find it is actually shut
Also on the same road at the moment is this from ViaMichelin with another weight limit at La Grave, the next village to the east from the tunnel.
Further information with this PDF