As always spotting is tolerated in Italy but not so easy like up there, so be carefull. Luni is a nice place and there is a 1 car park along the fence as just you cross the main rwy going to the Capitanerie di porto, on the left. You stop just in front of a gate in front of the rwy. Photography is good in the morning (in the afternoon you must go on the other side but did not find a nice place (did not look for...)).
I was going to this place only when the helis were moving and then left. I don't know if Carabinieri can come out and ask you to leave.
If you are not particularly lucky do not expect too much movement.
If you ask the capitanerie di porto in Advance for a visit it should be quite easy (at least some years ago). I have not email but you can look in the internet to find out the telephone or email....Good to ask for afternoon visit as they are parked in good position only then.
I had that time (05-2007) a 400d and a 35-350 and used alot at the long end:
hope this helps, ciao gp