Hey,
That's one of the thing about Pro Tools...is it hardware or is it software?
It's BOTH to my knowledge; it is a complete system from the ground up encompassing hardware and software. Their systems come in all sizes and flavors, ranging from the Digi001/M-Box and ProToolsLE at the bottom end all the way up to the big HD192 systems with PT6 and the DSP cards.
The advantage is that the hardware and software are designed to work with each other...the disadvantage is that once you get stuck into a Digidesign system, it is very difficult to get out because you have to get rid of EVERYTHING. Digidesign cards won't work with ASIO drivers, and you cannot use their cards under Windows except for simple 2 channel playback; Digidesign software won't work with cards that aren't Digidesign...
So, to answer your question, I don't think that you can use the Layla or the 1010 with any version of the ProTools software, except for maybe ProTools Free (which is a joke).
As for preamps...I'm not much of a preamp kind of guy, so I can only relay what people have told me: do not get the Digi001 just because it has preamps, they sound terrible, and you will eventually get different convertors. A co worker uses the Digi001, but purchased a Focusrite preamp and RME Hammerfall 8/8 convertor box and plugged it into the Digi001's ADAT interface because its own convertor box sounded so terrible. He's as happy as a clam now, but it cost him a lot of money!
Take care,
Nick