were you not suggesting a coalition would be likely if the PCs got a minority? That would be required for the Liberals to form government in that point, a formally vote of support from the NDP, no? The Liberals can't just go in front of the lieutenant governor and ask to form government without the NDP giving the governor confidence that they would actually be able to govern.
By default, in the absence of any agreement, if the government falls, the LG would be very likely to simply appoint Del Duca as Premier - assuming it's just after the election. More likely there'd be an agreement to support (which isn't binding) from the NDP to the Liberals. But in 1985 the agreement was made weeks before the non-confidence vote, in an attempt to get Premier Miller to resign rather than reconvening the legislature.
But I can't see the Liberals forming a coalition with the NDP. I don't think it's ever happened before anywhere in Canada. In a coalition, there would be both NDP and Liberals in cabinet.
If there's to be a coalition, I'd think it would be more likely PC-NDP - if Ford is willing to offer the NDP seats in cabinet to stay in power, and the Liberals won't, I wouldn't be shocked if the NDP took it. Ford is a lot more pragmatic than Miller ever seemed.
But I expect the outcome - barring any surge in PC support - would be a Liberal minority government, with support from the NDP.
We are drifting off-topic though I'm not sure what the NDP's opinion is on the Ontario Line (or much of anything really). Though I don't think they vehemently oppose the concept in the same way they did historically.