We don't know how they run as they haven't been made yet. They are taking pre-orders, OR pre-orders have already sold out before they arrived, so any new order is on back order until a 2cnd run delivery (very doubtful)
This is a popular novelty in G scale so some folks know that version already.
Ours might be as strong as a single motor switcher loco, or weak like a handcar or trolley. (It has couplers it seems, but looks more like a trolley and they don't show "a few" inline anywhere at B.mann. I thought I'd seen a string of these, but it may have been one of the RMT minis I'm actually thinking of)
These appeared in G sometime after RMT whimsical offerings dropped off. (I think... that's when I recall seeing them first) It's a blatent idea swipe of RMT shorties imo, but they filled a hole of need (whimsy) and where (G) RMT wasn't likely to enter soon if at all anyhow. (RMT is partially back with some new, more serious offerings and some left over old stock. The site still shows the cool whimsical mini locos and short passenger cars than ”had" to be the chickens that laid the Eggliner idea. Check their site out. (good quality at fair prices for fun items from nice people )
I figure the first Eggliner was either two observation car ends glued together, or an oval candy tin on an extra power truck ... I'm not too sure which.