Well, I guess I should save you some time here. So here's a bit of what I know....
i don't think its just those values, it's probably the BITS that matter
Actually, the value is just an index into a table. The bits mean nothing themselves. Here is the meaning of the table entries.
00 (0x00) "Fast Passible 1"
01 (0x01) "Impassible 2"
02 (0x02) "Slow Passible 1"
03 (0x03) "Slow Passible 2"
04 (0x04) "Medium Passible 1"
05 (0x05) "Medium Passible 2"
06 (0x06) "Impassible 1"
07 (0x07) "Fast Passible 2"
08 (0x08) "North Cliffs"
09 (0x09) "Cliffs - High side"
10 (0x0A) "Cliffs - Low Side"
11 (0x0B) "Vents and Fumaroles"
12 (0x0C) "zPad 12"
13 (0x0D) "zPad 13"
14 (0x0E) "zPad 14"
15 (0x0F) "zPad 15"
16 (0x10) "zPad 16"
17 (0x11) "zPad 17"
18 (0x12) "zPad 18"
19 (0x13) "zPad 19"
20 (0x14) "zPad 20"
21 (0x15) "Dozed Area"
22 (0x16) "Rubble"
23 (0x17) "Normal Wall"
24 (0x18) "Microbe Wall"
25 (0x19) "Lava Wall"
26 (0x1A) "Tube0"
27 (0x1B) "Tube1"
28 (0x1C) "Tube2"
29 (0x1D) "Tube3"
30 (0x1E) "Tube4"
31 (0x1F) "Tube5"
So yeah, that's how I know there is more than one value for tubes. But I've only ever seen 26 (0x1A) used. If you have any idea when the others are used, I'd love to hear about it. Anyways, that table really contains more than just the terrain type names. It also contains the movement rate for each vehicle track type. (I think anyways, haven't had much time to look into it. There might be more in the table too). (Also, you might see why I suspected different players get different tube values since there are 6 players and 6 tube types, but then the game really uses 7 players internally so I never really thought the idea plausible enough to bother proving wrong.)
If you're wondering about that odd value from the editor, I'd guess it's because we only really found this stuff out recently. Probably about a week ago (maybe two).
I found out, you can put a tube onto the gamemap (either with a map editor or with SetTile), and an earthworker is still able to build a tube on that very sqaure. This would also suggest the game does NOT recognise this "orginal" tile as a tube.
Most definately how it works. The value for the tile really means nothing to the game at all. It's just an index of which tile to display for that square. Even which one represents a tube is arbitrary. There is a structure that maps ranges of tiles to corresponding tube/wall/rublle/bulldozed tiles. Each terrain type (rock/lava rock/dirt) has it's own table, so that's why when you bulldoze/tube/etc. the background color of the terrain stays the right color. All the game does is check which terrain type the tile falls in (all terrain types are a consecutive run of tile indexes) and replace that tile index with the corresponding one in the table for bulldozed terrain (or tubes, but that's more complicated since the graphics are directional and depend on surrounding tubes).
So yeah, those tile values are simple, meaningless, indexes. If you were to change the tilesets, those values would be useless since the new graphics would (most likely) be in a different order.