I suppose the question is:
Can I do runstat on more than 1 table within a database at the same TIME, any concurrent problem ?
No problem in the system catalog tables.
But you might consider: with more than one table in a tablespace - this is not a problem of doing but who gets to read the pages first ... Still should not be a problem either, only for very fragmented data.
It does not make sense to run runstats twice and in parallel on the same table ...