Possible solution found. Instead of including a generated file I will try using:
In first ipython cell
Create html with embedded links for every line:
from Ipython.display import display HTML
for n, line in enumerate(logdata, 1):
display(HTML('<a id="line%06i">%s</b>' % (n, line)))
Click to scroll the cells output. This will create a scrolling html "div" section when there are many lines.
In another cell
I can create a link to scroll to line 22 for example by calling display again:
display(HTML('<a href="#line000022">go to line000022</a>'
I would prefer to get the cross document messaging for an embedded iframe working, but that solution eludes me.