yes you can but its a rough 12 step process
first you need 3 copys of GTA 2 for xbox and 1 for ps3. 2 xboxs and 1 ps3, 2 tvs with 3 video inputs on each, ok go get that then do the following...
1. hook up xbox 1 at your house, put gta BUT DONT LOAD IT YET.. this is importian.
2. bring PS3 and xbox 2 to your buddys house. your going to need 2 micro screw drivers 1 phillips 1 flat head and possibilby a drill.
3. hook PS3 up to your buddys power out let but NOT THE TV YET, its is also importain.
4. unscrew contoller 1 on ps3 complety apart and place contents on your table. repete same process with xbox controller. now you need tin foil a paper bag and 2 allen wrenchs.
5 spit into the paper bag and place on table next to you, we will get to this in a minute take contents from the 2nd controller you took apart and place them in the first contoller you took apart this may require slight drilling.
6. take contents from the other controller and place them in the bag you spit in with the 2 allen wrenches.. shake bag for exactly 8mins no more no less.
7.hook xbox 2 up to you buddys tv on video 2 BUT DO NOT HOOK UP POWER CORD YET.. this is importain like before.
8. take the tin foil and fold it into a open top box shape, the quality of the box is not nessassary as much as how deep it is as it does need to be aleast 3'' deep and 6'' wide.
9. hook PS3 up to TV on a video 1, and turn it on and load GTA when you start step 10
10. ok this is the hard part as GTA is loading on the PS3 you have to quicky load GTA on xbox 2 and get into a multiplayer game before it loads on the PS3. you can hook xbox power cord up now.
11.place PS3 in front of you buddys TV, place xbox behind it, the placement of the systems is very importian to the sucess of this. at this point you should be in a mulitplayer game so pick up controller 1 give it to you buddy run home and join game.
12. have you buddy dump contents from paper back into the tin box and then start the match.
sucess! you are now playing GTA crossplatform!! great job