How can I make a model of a single wire CAN bus cable?
I don't think the actual cable latency will be the issue. It's more likely to be the speed of the rising edges you get as the cable length increases. The capacitance of the cable will be of the order of 100&nbsp;pF/m for coax. I'm neglecting the resistance of the cable.

So, the RC time constant will be ~330&nbsp;ns at 1&nbsp;m and ~1300&nbsp;ns at 4&nbsp;m. Assuming that it takes maybe three RC time constants to reach the threshold voltage of the receiver, that's about 1&nbsp;µs/m.

So, even at 1&nbsp;m cable length, I think it'll struggle to work at 1&nbsp;Mbit/s (as the time to settle is approaching the bit-time). At 10&nbsp;kbit/s I can't see why it wouldn't work over longer cables.

-- Update -- 

I should also mention there are proper single-wire CAN physical layers available for use at low bit rates, for example the NXP NCV7356