I'm with Mr. Schmeelk. Just visually though, as I don't have one here, but appears to have some thought applied to it -vs--being a "get-er-done" job.
Too bad Frank Petit wasn't around to design this thing !!
.....Frank was the name of the man my Grandfather talked to from Lionel all the time. Same guy?? I think he was the one looked for, and found, my "X" set if you caught the post. Designer, huh...I often wish we had kept that outdated Rolodex another fifteen years past its prime... Trains were still boxed then, wasn't thinking about the train folks, & most listed had passed on, or we didn't know them.
I never came across a name for the fitting of tube that way. We would just say "shrink tube clamp" butted, seated, or on a nipple/ barb. They had been creeping into coin-op and HVAC since the 80's as a light duty option. With good tube, trimming, and fitment, it shouldn't be a regularly returning issue. When first encountered, it can be frustrating, like many new things, you get used to it. Auto companies use the method too.
On tubing, "FUEL" should be stated for the best chance at getting a tube that wont melt or become brittle. A Menards/H.Depot/Lowes should have something for weed wackers that fits. But as mentioned earlier on, the foreign suppliers sometimes worry more about getting a tube into a blister pack , than getting the right tube into a blister pack. (we can only blame ourselves America).
Silicone should be ok , but you may find it to be squirmy to work with. The frosted tube used; it looks like silicone to me. I did run across batches of Sil.tube that "split" suddenly under stress of harder curves. Normally thicker walled than other types for the ID used, its not as prone to kinking* (if it does, its usually stops flow 100%) My only issue was a situational one with an oversized nipple; silicone splits sooner when the ID is stretched open too far. *medical/dental equipment used it a lot.
For the 90º elbow an RC oriented hobby store should carry either brass and/or plastic "mini"-elbows rated for fuel use. The "Parker Store" are another possible source if near you. An industrial fitting specialty company with a very wide variety of connectors large and small. Sometimes pricey, but normally competitive for the quality handed to you IMO. [shop with time to look around at the variety, and newest plumbing ideas. Always a new surprise]
Other robotic and pneumatic supply houses may prove fruitful too.
I'm not sure of the present stance on this by Lionel today, but the old PW Lionel & MPC-L stated in print, to use Naptha (Zippo style lighter fluid for a little can, vs quart or gallon labeled Naptha) for cleaning their plastics.
I used it on all my toys as a kid. I don't remember totally ruining anything but a very dirty, light blue gondola. It has some weaker lettering today (be careful, and test,"Paint Warning", it will remove some paints/inks [given time to, maybe even loosen a modern glue?]. That said, to give you a general idea of how weak/strong it is, in my experience, paint doesn't suddenly start running down the sides, but after a few seconds, can begin to be rubbed off. Left alone to dry again, the paints resets. (After it dried well, a fast wipe with Naptha removed the light paint smears, without time for penetrating and disturbing the main lettering again).
My Grandfathers bench had a sealed can for Naptha rags, and it's odor was faintly in the air from near daily use, either filling the Zippo he carried, or cleaning a Lionel train car. Add that to Lucky Strike, coffee, ozone and smoke pellet scent, and your there...I mean here....here, but then. ?...you know.