I'm a bit confused by your question...
eSignal and MetaStock can be used together in either of or a combination of 2 ways...
1. eSignal RT data can be collected and stored in MetaStock folders + be archived to your hard drive. RT files are appended to your hard drive at your selected intervals and are displayed as "live" charts.
2. eSignal data from their servers can be imported live through Data On Demand Cache, and utilized by MetaStock.
I've done #1 mostly for years + each RTH session I load the ES and NQ all-session charts for overnight highs and lows.