Hi,
Yes you can summarize any network but, as long as you do not break the LSPs. In most practical cases this means Loopbacks should never, the rest can be summarized.
Actually with conditional label distribution you could restric LDP to only announce labels for the Loopback networks required. Thus from an MPLS point of view "the rest" of IP networks is irrelevant and could be summarized or even be suppressed.
Hope this helps! Please rate all posts.
Regards, Martin