It has been tried and doesn't work very well, even for low-density pinouts:

https://tomverbeure.github.io/2019/11/21/Z-tape.html

From the datasheet linked there, it looks like the minimum recommended spacing to ensure electrical isolation between adjacent conductors is 15 mil (0.4mm). In an example I found here [1], the pitch between BGA pins is 0.5 mm to 1.0 mm, with pad sizes roughly half of the pitch. So it looks like for the larger pitches, it might just work. 3M also says they'll do custom tape with better isolation, but that might just be more expensive than a reflow oven.

[1] https://www.nxp.com/docs/en/application-note/AN10778.pdf