Hi, just to share my experience it may be interesting to someone.

I was running TT in Abu Dhabi when the server maintenance started. I was in a charge, so a bit upset at first, I was improving my best and I decelerated in the last meters (to avoid my offline telemetry to keep in memory a 'wrong' lap) but then I decided to push anyway, so few minutes later I improved it again. And here I tell you what I did, no idea if it means something, perhaps the laptime would be registered as soon as the server gets up the same, but in this way it worked:

- first of all after my new best has been achieved I continued to play with the new delta (comparing with the new sectors) in the same session;

- the server was down but RaceNet was live, I checked Time Trial and there the previous best was still on, as expected;

- I paused the game during a lap without leaving the session;

- after the server was back running I went to the garage, the connection was on and immediately my new best lap has been registered.

Nothing more 

I remember in an old topic there was a bit of confusion about and the most were assuming a laptime is registered only if the server is live when the lap is completed, while I checked today it works differently 

Cheers,

Nuv