B767 First Officer reports problems with the BT VOR departing LFPG on the L'AIGLE 1Y from Runway 27L. A track deviation to the west occured before correcting to the north.

Narrative

Given the L'Aigle Runway 27L 1Y departure; after passing CGN266R 1.5 DME; the BT 329R would not intercept (or at least 'come alive') continued on more westerly heading to intercept; since the 329R radial was still showing ahead of the aircraft (full scale). Returned BT 108.6 and 329R in the VOR panel when I realized that this was very unusual. No sooner had I reselected 108.8; when the VOR needle went full scale deflection down; indicating we had passed the BT 329R. Captain immediately turned to a northerly heading (about 340) to re-intercept the BT 329R. No sooner had he rolled out onto intercept heading when ATC gave us radar vectors back to a 270 degree heading. Correct BT frequency was confirmed at gate and before taking the runway; so why the full scale deflections in the time it took to rotate the VOR frequency knob 2 clicks clockwise; and 2 clicks counterclockwise? As a side note; we were informed that the 'Le Bourget Air show Performance' was occurring at our expected departure; (although that should have nothing to do with navigation performance). No mention of this was made by ATC just our own critique regarding navigation performance and noise abatement adherence.