According to the guide yes I viewed it on www.bt.co.uk/userguides down load a guide so you have one safe in your computer.
I very much doubt each base phones will work as you would like. I would assume the handset will only connect to the line of the base station it's near or on. but who knows I know a man who does BT.
Check with BT. 0870 604 8047 quoting synergy 3505 you've nothing to lose. If you can't do what you require what about the following idea .
Have Two base stations and two additional hansets.
Leave each base station hanset in place .
Place next to/near base station for line1 the additional handset and cradle serving line 2.
Then next to base station for line 2 place the additional handset and cradle that serves line 1.
You can do this providing of course you can keep the additional hansets in range of their default base stations. eg: additional hanset of line 1 in range of line 1 base station. set up this way each line is covered without having to go from one room/office to another. Remember though the additional hansets have a shorter range indoors of around 50mt.
BOB
February 2005